feat: impl show index and show columns

[killme2008]

I hereby agree to the terms of the GreptimeDB CLA.

Refer to a related PR or issue link (optional)

#3354

What's changed and what's your intention?

Impl SHOW COLUMNS FROM [tbl] and SHOW INDEX FROM [tbl].

• https://dev.mysql.com/doc/refman/8.0/en/show-columns.html
• https://dev.mysql.com/doc/refman/8.0/en/show-index.html

For example:

SHOW COLUMNS FROM system_metrics;

+-------------+----------------------+------+------------+---------------------+-------+
| Field       | Type                 | Null | Key        | Default             | Extra |
+-------------+----------------------+------+------------+---------------------+-------+
| cpu_util    | Float64              | Yes  |            |                     |       |
| disk_util   | Float64              | Yes  |            |                     |       |
| host        | String               | Yes  | PRI        |                     |       |
| idc         | String               | Yes  | PRI        |                     |       |
| memory_util | Float64              | Yes  |            |                     |       |
| ts          | TimestampMillisecond | No   | TIME INDEX | current_timestamp() |       |
+-------------+----------------------+------+------------+---------------------+-------+

SHOW INDEX FROM system_metrics;

+----------------+------------+------------+--------------+-------------+-----------+-------------+----------+--------+------+----------------------------+---------+---------------+---------+------------+
| Table          | Non_unique | Key_name   | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type                 | Comment | Index_comment | Visible | Expression |
+----------------+------------+------------+--------------+-------------+-----------+-------------+----------+--------+------+----------------------------+---------+---------------+---------+------------+
| system_metrics | 1          | PRIMARY    | 1            | host        | A         |             |          |        | YES  | greptime-inverted-index-v1 |         |               | YES     |            |
| system_metrics | 1          | PRIMARY    | 2            | idc         | A         |             |          |        | YES  | greptime-inverted-index-v1 |         |               | YES     |            |
| system_metrics | 1          | TIME INDEX | 1            | ts          | A         |             |          |        | NO   | greptime-inverted-index-v1 |         |               | YES     |            |
+----------------+------------+------------+--------------+-------------+-----------+-------------+----------+--------+------+----------------------------+---------+---------------+---------+------------+

Checklist

• I have written the necessary rustdoc comments.
• I have added the necessary unit tests and integration tests.
• This PR does not require documentation updates.

[codecov]

Codecov Report

Attention: Patch coverage is 51.77305% with 204 lines in your changes are missing coverage. Please review.

Project coverage is 84.88%. Comparing base (e3b37ee) to head (a6077a6).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3577      +/-   ##
==========================================
- Coverage   85.34%   84.88%   -0.46%     
==========================================
  Files         931      931              
  Lines      154619   155023     +404     
==========================================
- Hits       131956   131593     -363     
- Misses      22663    23430     +767     

[killme2008]

@waynexia @Taylor-lagrange @tisonkun Help to take a look, thank you.

[tisonkun]

Generally look good.