feat: improve observability for subscription/cursor SHOW commands

[hzxa21]

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What's changed and what's your intention?

Limitations for subscription/cursor SHOW commands prior to this PR:

• Output only contains the name of the subscription and cursor.
• SHOW CURSORS / SHOW SUBSCRIPTION CURSORS only show cursor names in the current session where the show command is run.

After this PR:

• SHOW CURSORS / SHOW SUBSCRIPTION CURSORS output all cursor information across active sessions in the same frontend node.
• SHOW CURSORS outputs Id | User | Host | Database | Cursor Name
• SHOW SUBSCRIPTION CURSORS outputs Id | User | Host | Database | Cursor Name | Subscription Name | State | Idle Duration Ms
• SHOW SUBSCRIPTIONS outputs Name | Retention Seconds

Checklist

• I have written necessary rustdoc comments
• I have added necessary unit tests and integration tests
• I have added test labels as necessary. See details.
• I have added fuzzing tests or opened an issue to track them. (Optional, recommended for new SQL features Sqlsmith: Sql feature generation #7934).
• My PR contains breaking changes. (If it deprecates some features, please create a tracking issue to remove them in the future).
• All checks passed in ./risedev check (or alias, ./risedev c)
• My PR changes performance-critical code. (Please run macro/micro-benchmarks and show the results.)

• My PR contains critical fixes that are necessary to be merged into the latest release. (Please check out the details)

Documentation

• My PR needs documentation updates. (Please use the Release note section below to summarize the impact on users)

Release note

Enhance SHOW command for subscription and subscription cursor:

• SHOW CURSORS / SHOW SUBSCRIPTION CURSORS output all cursor information across active sessions in the same frontend node.
• SHOW CURSORS outputs Id | User | Host | Database | Cursor Name
• SHOW SUBSCRIPTION CURSORS outputs Id | User | Host | Database | Cursor Name | Subscription Name | State | Idle Duration Ms
• SHOW SUBSCRIPTIONS outputs Name | Retention Seconds

[hzxa21]

Examples:

dev=> create subscription test_subscription from test_table with (retention = '1d');
CREATE_SUBSCRIPTION
dev=> show subscriptions;
       Name        | Retention Seconds 
-------------------+-------------------
 test_subscription |             86400
(1 row)

-- session 1
dev=> declare session1_cursor subscription cursor for test_subscription;
DECLARE_CURSOR

-- session 2
dev=> declare session2_cursor subscription cursor for test_subscription;
DECLARE_CURSOR

-- session 3
dev=> show subscription cursors;
 Id | User |      Host       | Database |   Cursor Name   | Subscription Name |                                      State                                       | Idle Duration Ms 
----+------+-----------------+----------+-----------------+-------------------+----------------------------------------------------------------------------------+------------------
 1  | root | 127.0.0.1:47777 | dev      | session2_cursor | test_subscription | InitLogStoreQuery { seek_timestamp: 7317774995947520, expected_timestamp: None } |             5378
 0  | root | 127.0.0.1:47775 | dev      | session1_cursor | test_subscription | InitLogStoreQuery { seek_timestamp: 7317774079950848, expected_timestamp: None } |            19355
(2 rows)

[xxhZs]

lgtm