planner: fix trace cost detail performance regression

[Yisaer]

Signed-off-by: yisaer [email protected]

What problem does this PR solve?

Issue Number: close #37096

Problem Summary:

What is changed and how it works?

Before:

BenchmarkTableScan-4   	    2829	    383439 ns/op

After:

BenchmarkTableScan-4   	    3663	    277817 ns/op

Check List

Tests

• No code

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:

• hawkingrei
• tiancaiamao

To complete the pull request process, please ask the reviewers in the list to review by filling /cc @reviewer in the comment.
After your PR has acquired the required number of LGTMs, you can assign this pull request to the committer in the list by filling /assign @committer in the comment to help you merge this pull request.

The full list of commands accepted by this bot can be found here.

Reviewer can indicate their review by submitting an approval review.
Reviewer can cancel approval by submitting a request changes review.

[sre-bot]

Code Coverage Details: https://codecov.io/github/pingcap/tidb/commit/378674eeca1d8140c48f4efd5c48b5d1a543200a

[hawkingrei]

/merge

[ti-chi-bot]

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

Commit hash: 02fbd65

[Yisaer]

/merge

[sre-bot]

TiDB MergeCI notify

CI Name	Result	Duration	Compare with Parent commit
idc-jenkins-ci/integration-cdc-test	🟢 all 36 tests passed	30 min	Existing passed
idc-jenkins-ci-tidb/integration-common-test	🟢 all 17 tests passed	14 min	Existing passed
idc-jenkins-ci-tidb/common-test	🟢 all 11 tests passed	13 min	Existing passed
idc-jenkins-ci-tidb/tics-test	🟢 all 1 tests passed	6 min 31 sec	Existing passed
idc-jenkins-ci-tidb/integration-ddl-test	🟢 all 6 tests passed	6 min 5 sec	Existing passed
idc-jenkins-ci-tidb/sqllogic-test-2	🟢 all 28 tests passed	5 min 48 sec	Existing passed
idc-jenkins-ci-tidb/sqllogic-test-1	🟢 all 26 tests passed	5 min 14 sec	Existing passed
idc-jenkins-ci-tidb/mybatis-test	🟢 all 1 tests passed	3 min 29 sec	Existing passed
idc-jenkins-ci-tidb/integration-compatibility-test	🟢 all 1 tests passed	3 min 6 sec	Existing passed
idc-jenkins-ci-tidb/plugin-test	🟢 build success, plugin test success	4min	Existing passed