variable: revise TiDBStatsCacheMemQuota settting code

[Yisaer]

Signed-off-by: yisaer [email protected]

What problem does this PR solve?

Issue Number: ref #34052

Problem Summary:

What is changed and how it works?

revise TiDBStatsCacheMemQuota settting code by moving code into SetGlobal

Check List

Tests

• Manual test (add detailed scripts or steps below)

I manually tested set global tidb_stats_cache_mem_quota, it still work

Release note

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

None

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• chrysan
• morgo

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[sre-bot]

Code Coverage Details: https://codecov.io/github/pingcap/tidb/commit/bbe76069f244cbf22203b94e627a0cdda7bcac35

[morgo]

Nice work! We should consider using this same trick in the other cases where we need domain in sysvars. It will simplify the sysvar_cache code.

[Yisaer]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: b6e189f

[hawkingrei]

/run-mysql-test

[hawkingrei]

/run-mysql-test

[hawkingrei]

/run-mysql-test

[sre-bot]

TiDB MergeCI notify

🔴 Bad News! [1] CI still failing after this pr merged.
These failed integration tests don't seem to be introduced by the current PR.

CI Name	Result	Duration	Compare with Parent commit
idc-jenkins-ci-tidb/integration-common-test	🔴 failed 3, success 8, total 11	9 min 25 sec	Existing failure
idc-jenkins-ci/integration-cdc-test	🟢 all 34 tests passed	26 min	Existing passed
idc-jenkins-ci-tidb/tics-test	🟢 all 1 tests passed	10 min	Existing passed
idc-jenkins-ci-tidb/sqllogic-test-1	🟢 all 26 tests passed	6 min 47 sec	Existing passed
idc-jenkins-ci-tidb/sqllogic-test-2	🟢 all 28 tests passed	6 min 29 sec	Existing passed
idc-jenkins-ci-tidb/integration-ddl-test	🟢 all 6 tests passed	6 min 8 sec	Existing passed
idc-jenkins-ci-tidb/common-test	🟢 all 12 tests passed	5 min 17 sec	Existing passed
idc-jenkins-ci-tidb/mybatis-test	🟢 all 1 tests passed	3 min 31 sec	Existing passed
idc-jenkins-ci-tidb/integration-compatibility-test	🟢 all 1 tests passed	3 min 14 sec	Existing passed
idc-jenkins-ci-tidb/plugin-test	🟢 build success, plugin test success	4min	Existing passed