[fix](parser) Add NULL_TYPE support to Nereids parser grammar

[Baymine]

What problem does this PR solve?

Issue Number: close #xxx

Related PR: #xxx

Problem Summary:
Broker load tasks fail with a SyntaxParseException when the load statement contains CASE expressions that return NULL values. The error occurs because the Nereids parser grammar doesn't recognize null_type as a valid data type keyword, even though the DataType parsing logic already supports it.

Error Message:

org.apache.doris.nereids.exceptions.SyntaxParseException:
mismatched input 'null_type' expecting {'AGG_STATE', 'ALL', 'ARRAY', 'BIGINT', ...}

Case statement

 LOAD LABEL test_load
 (
     DATA INFILE("hdfs://namenode:9000/path/to/data.parquet")
     INTO TABLE test_load_table
     FORMAT AS "PARQUET"
     (dt, order_id, parent_order_id, amount, deal_flag)
     SET
     (
         status = CAST(COALESCE(deal_flag, '0') AS INT),
         parent_order_id = CASE
             WHEN deal_flag = '1' THEN parent_order_id
             ELSE null
         END
     )
 )
 WITH BROKER 'hdfs_broker';

Release note

None

Check List (For Author)

• Test

  • Regression test
  • Unit Test
  • Manual test (add detailed scripts or steps below)
  • No need to test or manual test. Explain why:
    • This is a refactor/code format and no logic has been changed.
    • Previous test can cover this change.
    • No code files have been changed.
    • Other reason

• Behavior changed:

  • No.
  • Yes.

• Does this need documentation?

  • No.
  • Yes.

Check List (For Reviewer who merge this PR)

• Confirm the release note
• Confirm test cases
• Confirm document
• Add branch pick label

[Thearas]

Thank you for your contribution to Apache Doris.
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Please clearly describe your PR:

1. What problem was fixed (it's best to include specific error reporting information). How it was fixed.
2. Which behaviors were modified. What was the previous behavior, what is it now, why was it modified, and what possible impacts might there be.
3. What features were added. Why was this function added?
4. Which code was refactored and why was this part of the code refactored?
5. Which functions were optimized and what is the difference before and after the optimization?

[Baymine]

run buildall

[doris-robot]

TPC-H: Total hot run time: 31473 ms

machine: 'aliyun_ecs.c7a.8xlarge_32C64G'
scripts: https://github.com/apache/doris/tree/master/tools/tpch-tools
Tpch sf100 test result on commit ae611d6cc3a638a1927123fb1dcbebaebd2fc339, data reload: false

------ Round 1 ----------------------------------
q1	17633	4138	4054	4054
q2	2045	356	243	243
q3	10137	1275	732	732
q4	10195	782	311	311
q5	7536	2088	1847	1847
q6	190	175	142	142
q7	939	801	674	674
q8	9280	1411	1189	1189
q9	4845	4661	4542	4542
q10	6749	1776	1402	1402
q11	489	310	279	279
q12	710	785	571	571
q13	17793	3822	3086	3086
q14	311	289	274	274
q15	597	505	509	505
q16	681	695	641	641
q17	657	815	486	486
q18	6722	6278	6342	6278
q19	1238	996	616	616
q20	386	357	257	257
q21	3069	2449	2361	2361
q22	1075	998	983	983
Total cold run time: 103277 ms
Total hot run time: 31473 ms

----- Round 2, with runtime_filter_mode=off -----
q1	4090	4016	4048	4016
q2	336	411	318	318
q3	2097	2636	2179	2179
q4	1327	1774	1365	1365
q5	4097	4020	3990	3990
q6	211	170	133	133
q7	1862	1809	1710	1710
q8	2907	2576	2492	2492
q9	7172	7203	7224	7203
q10	2671	2741	2253	2253
q11	557	475	444	444
q12	754	795	656	656
q13	3808	4099	3678	3678
q14	289	306	277	277
q15	550	510	533	510
q16	703	755	626	626
q17	1163	1282	1373	1282
q18	8127	7880	7759	7759
q19	920	973	943	943
q20	1973	2146	1943	1943
q21	4936	4536	4397	4397
q22	1115	1129	1034	1034
Total cold run time: 51665 ms
Total hot run time: 49208 ms

[doris-robot]

TPC-DS: Total hot run time: 173910 ms

machine: 'aliyun_ecs.c7a.8xlarge_32C64G'
scripts: https://github.com/apache/doris/tree/master/tools/tpcds-tools
TPC-DS sf100 test result on commit ae611d6cc3a638a1927123fb1dcbebaebd2fc339, data reload: false

query5	4431	619	488	488
query6	335	221	210	210
query7	4218	454	263	263
query8	356	253	240	240
query9	8687	2922	2896	2896
query10	550	402	344	344
query11	15233	15354	15917	15354
query12	184	118	114	114
query13	1293	531	420	420
query14	6217	3167	2909	2909
query14_1	2741	2788	2761	2761
query15	230	194	184	184
query16	1063	492	441	441
query17	1518	686	602	602
query18	2540	433	341	341
query19	224	226	189	189
query20	122	123	117	117
query21	203	133	112	112
query22	3873	3990	3784	3784
query23	16240	15837	15537	15537
query23_1	15502	15444	15432	15432
query24	7161	1523	1162	1162
query24_1	1156	1172	1143	1143
query25	536	447	394	394
query26	1242	272	151	151
query27	2753	444	275	275
query28	4509	2233	2171	2171
query29	736	502	407	407
query30	302	232	193	193
query31	806	599	564	564
query32	78	69	69	69
query33	516	320	294	294
query34	915	865	530	530
query35	706	779	668	668
query36	899	885	776	776
query37	142	97	79	79
query38	2753	2672	2650	2650
query39	791	750	727	727
query39_1	721	712	696	696
query40	216	136	114	114
query41	69	59	60	59
query42	98	101	102	101
query43	442	470	411	411
query44	1292	739	745	739
query45	182	182	173	173
query46	834	966	569	569
query47	1441	1492	1392	1392
query48	314	335	239	239
query49	602	436	343	343
query50	621	266	212	212
query51	3768	3798	3729	3729
query52	107	107	91	91
query53	287	325	267	267
query54	282	267	253	253
query55	82	76	77	76
query56	311	308	342	308
query57	1052	1013	939	939
query58	268	253	250	250
query59	2125	2238	2093	2093
query60	325	327	316	316
query61	154	149	158	149
query62	375	351	309	309
query63	293	266	264	264
query64	4927	1220	954	954
query65	3810	3780	3718	3718
query66	1453	431	319	319
query67	15609	15504	15505	15504
query68	2399	1095	797	797
query69	443	359	316	316
query70	937	941	918	918
query71	329	312	275	275
query72	5319	2424	3317	2424
query73	599	717	323	323
query74	8698	8756	8545	8545
query75	2768	2795	2428	2428
query76	2269	1053	654	654
query77	364	374	306	306
query78	9812	9973	9199	9199
query79	2219	880	592	592
query80	1672	581	480	480
query81	550	262	228	228
query82	987	151	114	114
query83	331	250	244	244
query84	252	113	97	97
query85	908	517	443	443
query86	408	295	292	292
query87	2861	2854	2735	2735
query88	3504	2571	2556	2556
query89	391	350	316	316
query90	2001	161	168	161
query91	172	156	143	143
query92	89	71	72	71
query93	1070	918	538	538
query94	646	344	302	302
query95	593	373	312	312
query96	635	507	233	233
query97	2310	2398	2301	2301
query98	217	204	196	196
query99	590	585	506	506
Total cold run time: 249062 ms
Total hot run time: 173910 ms

[doris-robot]

ClickBench: Total hot run time: 26.86 s

machine: 'aliyun_ecs.c7a.8xlarge_32C64G'
scripts: https://github.com/apache/doris/tree/master/tools/clickbench-tools
ClickBench test result on commit ae611d6cc3a638a1927123fb1dcbebaebd2fc339, data reload: false

query1	0.05	0.04	0.04
query2	0.10	0.05	0.04
query3	0.25	0.09	0.09
query4	1.60	0.12	0.11
query5	0.26	0.25	0.25
query6	1.14	0.66	0.64
query7	0.03	0.02	0.03
query8	0.05	0.04	0.04
query9	0.57	0.50	0.49
query10	0.56	0.56	0.56
query11	0.15	0.10	0.10
query12	0.15	0.11	0.11
query13	0.62	0.58	0.59
query14	0.97	0.93	0.93
query15	0.79	0.78	0.78
query16	0.42	0.39	0.40
query17	1.06	1.05	1.06
query18	0.22	0.22	0.21
query19	1.91	1.91	1.88
query20	0.02	0.01	0.01
query21	15.44	0.24	0.15
query22	5.04	0.05	0.05
query23	16.03	0.28	0.10
query24	2.72	0.30	0.54
query25	0.09	0.05	0.08
query26	0.15	0.13	0.14
query27	0.09	0.07	0.07
query28	4.39	1.06	0.88
query29	12.53	3.94	3.13
query30	0.28	0.13	0.12
query31	2.81	0.63	0.40
query32	3.24	0.56	0.46
query33	2.98	2.98	3.07
query34	15.96	5.09	4.43
query35	4.51	4.42	4.42
query36	0.66	0.50	0.49
query37	0.11	0.07	0.07
query38	0.07	0.04	0.04
query39	0.04	0.03	0.03
query40	0.17	0.15	0.14
query41	0.09	0.04	0.03
query42	0.05	0.03	0.03
query43	0.04	0.04	0.04
Total cold run time: 98.41 s
Total hot run time: 26.86 s

[hello-stephen]

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[zclllyybb]

where does null_type present in your stmt?