*: Add system variable tidb_session_alias to log a custom field session_alias in session log

[lcwangchao]

What problem does this PR solve?

Issue Number: close #46071

What is changed and how it works?

A new system variable tidb_session_alias with session scope is added. After this PR, we can trace some session in log identified by this field. for example:

> set @@tidb_session_alias='custom_session1';
> select * from tnoexist; -- select from a not exist table

Some log will be printed and you can see session_alias in it.

[2023/08/14 17:48:50.766 +08:00] [WARN] [session.go:2255] ["compile SQL failed"] [conn=2097154] [session_alias=custom_session1] [error="[schema:1146]Table 'test.tnoexist' doesn't exist"] [SQL="select * from tnoexist"]
[2023/08/14 17:48:50.766 +08:00] [INFO] [conn.go:1096] ["command dispatched failed"] [conn=2097154] [session_alias=custom_session1] [connInfo="id:2097154, addr:127.0.0.1:61498 status:10, collation:utf8_general_ci, user:root"] [command=Query] [status="inTxn:0, autocommit:1"] [sql="select * from tnoexist"] [txn_mode=PESSIMISTIC] [timestamp=0] [err="[schema:1146]Table 'test.tnoexist' doesn't exist"]

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

Add system variable `tidb_session_alias` to log a custom field `session_alias` in session log

[codecov]

Codecov Report

Merging #46072 (f5a6976) into master (5f41a0f) will decrease coverage by 2.0678%.
Report is 14 commits behind head on master.
The diff coverage is 80.5825%.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #46072        +/-   ##
================================================
- Coverage   74.7886%   72.7208%   -2.0678%     
================================================
  Files          1297       1306         +9     
  Lines        398784     400621      +1837     
================================================
- Hits         298245     291335      -6910     
- Misses        81155      90790      +9635     
+ Partials      19384      18496       -888     

Flag	Coverage Δ
integration	25.5950% <31.2500%> (-20.6533%)	⬇️
unit	73.4025% <80.5825%> (+0.0241%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
dumpling	54.0444% <ø> (ø)
parser	85.0765% <0.0000%> (ø)
br	47.8865% <ø> (-16.6485%)	⬇️

[bb7133]

LGTM

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2023-08-15 10:35:13.299620691 +0000 UTC m=+627277.848636663: ☑️ agreed by CbcWestwolf.
• 2023-08-18 03:27:36.041872637 +0000 UTC m=+860820.590888624: ☑️ agreed by bb7133.

[lcwangchao]

/approve

[easonn7]

/approve

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: bb7133, CbcWestwolf, easonn7, lcwangchao

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Needs approval from an approver in each of these files:

• OWNERS [CbcWestwolf,bb7133,lcwangchao]
• sessionctx/variable/OWNERS [easonn7]

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[lcwangchao]

/retest

[tiprow]

@lcwangchao: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
tiprow_fast_test	f5a6976	link	true	/test tiprow_fast_test

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