[test](ctas) add some ut for testing varchar length in ctas

[morningman]

Proposed changes

1. If derived from a origin column, eg: create table tbl1 as select col1 from tbl2, the length will be same os the origin column.
2. If derived from a function, eg: create table tbl1 as select func(col1) from tbl2, the length will be 65533.
3. If derived from a constant value, eg: create table tbl1 as select "abc" from tbl2, the length will be 65533.

Further comments

If this is a relatively large or complex change, kick off the discussion at dev@doris.apache.org by explaining why you chose the solution you did and what alternatives you considered, etc...

[morningman]

run buildall

[github-actions]

PR approved by anyone and no changes requested.

[hello-stephen]

(From new machine)TeamCity pipeline, clickbench performance test result:
the sum of best hot time: 46 seconds
stream load tsv: 512 seconds loaded 74807831229 Bytes, about 139 MB/s
stream load json: 20 seconds loaded 2358488459 Bytes, about 112 MB/s
stream load orc: 65 seconds loaded 1101869774 Bytes, about 16 MB/s
stream load parquet: 32 seconds loaded 861443392 Bytes, about 25 MB/s
insert into select: 29.3 seconds inserted 10000000 Rows, about 341K ops/s
storage size: 17162193034 Bytes

[xiaokang]

LGTM

[github-actions]

PR approved by at least one committer and no changes requested.