statistics: revise statscache lru implementation

[Yisaer]

Signed-off-by: yisaer disxiaofei@163.com

What problem does this PR solve?

Issue Number: ref #34052

Problem Summary:

What is changed and how it works?

revise statscache lru implementation and introduce is_index in cacheItem

Check List

Tests

• Unit test

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:

• JmPotato
• xuyifangreeneyes

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[sre-bot]

Code Coverage Details: https://codecov.io/github/pingcap/tidb/commit/4ed8f5984bcfc64f2a5d7b7592ddb47ca824d7fc

[Yisaer]

/merge

[ti-chi-bot]

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

Commit hash: c400523

[Yisaer]

/run-mysql-test

[Yisaer]

/run-mysql-test

[Yisaer]

/run-mysql-test

[sre-bot]

TiDB MergeCI notify

✅ Well Done! New fixed [1] after this pr merged.

CI Name	Result	Duration	Compare with Parent commit
idc-jenkins-ci-tidb/integration-common-test	✅ all 11 tests passed	14 min	Fixed
idc-jenkins-ci/integration-cdc-test	🟢 all 34 tests passed	36 min	Existing passed
idc-jenkins-ci-tidb/tics-test	🟢 all 1 tests passed	11 min	Existing passed
idc-jenkins-ci-tidb/mybatis-test	🟢 all 1 tests passed	6 min 41 sec	Existing passed
idc-jenkins-ci-tidb/common-test	🟢 all 12 tests passed	6 min 22 sec	Existing passed
idc-jenkins-ci-tidb/integration-ddl-test	🟢 all 6 tests passed	6 min 7 sec	Existing passed
idc-jenkins-ci-tidb/sqllogic-test-2	🟢 all 28 tests passed	5 min 46 sec	Existing passed
idc-jenkins-ci-tidb/sqllogic-test-1	🟢 all 26 tests passed	5 min 36 sec	Existing passed
idc-jenkins-ci-tidb/integration-compatibility-test	🟢 all 1 tests passed	3 min 5 sec	Existing passed
idc-jenkins-ci-tidb/plugin-test	🟢 build success, plugin test success	4min	Existing passed