[fix](doc) DESC-TABLE.md en: backport zh-only examples (Comment column, DESC ALL)

[boluor]

Summary

The ZH page for DESC-TABLE documents two examples that the EN page is missing:

1. SET show_column_comment_in_describe = true + DESC test_table — surfaces the Comment column. The session variable was introduced in 3.0.7 and is already described in the EN Return-Value section (line 59), but the EN page never exemplifies it.
2. DESC test_table ALL — returns the schema across all indexes, including IndexName, IndexKeysType, InternalType, Visible, DefineExpr, WhereClause.

Translated both blocks to English and added them under the existing example 1. The expected outputs were captured directly from a fresh Doris 4.1.1 cluster against the page's CREATE TABLE schema, so IndexKeysType = UNIQUE_KEYS to match UNIQUE KEY(user_id) (avoiding a stale DUP_KEYS value).

Verification

mysql> SET show_column_comment_in_describe=true;
mysql> DESC test_table;
+---------+-------------+------+-------+---------+-------+----------+
| Field   | Type        | Null | Key   | Default | Extra | Comment  |
+---------+-------------+------+-------+---------+-------+----------+
| user_id | bigint      | No   | true  | NULL    |       | Key1     |
| name    | varchar(20) | Yes  | false | NULL    | NONE  | username |
| age     | int         | Yes  | false | NULL    | NONE  | user_age |
+---------+-------------+------+-------+---------+-------+----------+

mysql> DESC test_table ALL;
+------------+---------------+---------+-------------+--------------+------+-------+---------+-------+---------+------------+-------------+
| IndexName  | IndexKeysType | Field   | Type        | InternalType | Null | Key   | Default | Extra | Visible | DefineExpr | WhereClause |
+------------+---------------+---------+-------------+--------------+------+-------+---------+-------+---------+------------+-------------+
| test_table | UNIQUE_KEYS   | user_id | bigint      | bigint       | No   | true  | NULL    |       | true    |            |             |
|            |               | name    | varchar(20) | varchar(20)  | Yes  | false | NULL    | NONE  | true    |            |             |
|            |               | age     | int         | int          | Yes  | false | NULL    | NONE  | true    |            |             |
+------------+---------------+---------+-------------+--------------+------+-------+---------+-------+---------+------------+-------------+

Related

• PR [fix](doc) zh: unix-timestamp missing semicolon; DESC-TABLE wrong db qualifier and stale IndexKeysType #3831 fixes the corresponding zh-side issues (demo. qualifier, stale DUP_KEYS) on the same examples. This PR adds the EN equivalents so the two language versions stay in sync.

Test plan

• Verified the EN expected output exactly matches Doris 4.1.1 cluster output
• IndexKeysType matches the schema's UNIQUE KEY (no copy-paste stale value)
• Page renders correctly (no fence/markdown issues)

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