executor: fix incorrect runtime stats when there are applys

[time-and-fate]

What problem does this PR solve?

Issue Number: close #35911 ref #35889

Problem Summary: please see #35911 for the incorrect behavior.

1. The concurrency of runtime stats of IndexLookUp and IndexMerge is aggregated in the Merge() method. This is different from other operators.
2. If it's in the probe side of an Apply, an executor may be reused (be Open()ed and Close()ed multiple times), so the runtime stats for display should be the aggregated sum of them.
   But for HashAgg, IndexLookUp, and IndexMerge, we incorrectly aggregated two times, which makes the numbers in the runtime stats larger than the correct ones:
   1. For each execution, the runtime stats is not reset, which means we aggregated all information into one runtime stats.
   2. For each execution, we also register them once more, as if there are new runtime stats for each execution.

What is changed and how it works?

1. Do not aggregate the concurrency in the Merge() method.
2. Reset runtime stats for each execution for HashAgg, IndexLookUp, and IndexMerge.

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.

None

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[REVIEW NOTIFICATION]

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• guo-shaoge
• wshwsh12

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Code Coverage Details: https://codecov.io/github/pingcap/tidb/commit/1111016642d249d07b8927d044dba0ffab0b9764

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/merge

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/run-mysql-test

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/merge cancel

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/merge

[ti-chi-bot]

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

Commit hash: 1111016

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/run-check_dev_2

[sre-bot]

TiDB MergeCI notify

CI Name	Result	Duration	Compare with Parent commit
idc-jenkins-ci/integration-cdc-test	🟢 all 35 tests passed	25 min	Existing passed
idc-jenkins-ci-tidb/integration-common-test	🟢 all 11 tests passed	22 min	Existing passed
idc-jenkins-ci-tidb/common-test	🟢 all 12 tests passed	13 min	Existing passed
idc-jenkins-ci-tidb/sqllogic-test-2	🟢 all 28 tests passed	5 min 30 sec	Existing passed
idc-jenkins-ci-tidb/integration-ddl-test	🟢 all 6 tests passed	5 min 22 sec	Existing passed
idc-jenkins-ci-tidb/sqllogic-test-1	🟢 all 26 tests passed	5 min 12 sec	Existing passed
idc-jenkins-ci-tidb/tics-test	🟢 all 1 tests passed	5 min 1 sec	Existing passed
idc-jenkins-ci-tidb/integration-compatibility-test	🟢 all 1 tests passed	3 min 1 sec	Existing passed
idc-jenkins-ci-tidb/mybatis-test	🟢 all 1 tests passed	2 min 51 sec	Existing passed
idc-jenkins-ci-tidb/plugin-test	🟢 build success, plugin test success	4min	Existing passed