executor: reduce a place of object allocation for HashAggExec

[tiancaiamao]

What problem does this PR solve?

Issue Number: close #37299

Problem Summary:

What is changed and how it works?

The parameter for UpdatePartialResult is []chunk.Row, but there is only one row here.
[]chunkRow{row} cause unnecessary object allocation.

Before:

After:

The runtime.newobject disappear after the change.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)

Run tpch16 and capture the flamegraph

• 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

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• hawkingrei
• xhebox

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[ti-chi-bot]

Code Coverage Details: https://codecov.io/github/pingcap/tidb/commit/504a8fc9dd134c7a2da7a0b1ac4171e9da8641b2

[xhebox]

/merge

[ti-chi-bot]

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

Commit hash: e360274

[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/integration-cdc-test	✅ all 36 tests passed	35 min	Fixed
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	9 min 51 sec	Existing passed
idc-jenkins-ci-tidb/integration-ddl-test	🟢 all 6 tests passed	6 min 15 sec	Existing passed
idc-jenkins-ci-tidb/sqllogic-test-2	🟢 all 28 tests passed	5 min 44 sec	Existing passed
idc-jenkins-ci-tidb/sqllogic-test-1	🟢 all 26 tests passed	5 min 25 sec	Existing passed
idc-jenkins-ci-tidb/mybatis-test	🟢 all 1 tests passed	4 min 6 sec	Existing passed
idc-jenkins-ci-tidb/integration-compatibility-test	🟢 all 1 tests passed	3 min 13 sec	Existing passed
idc-jenkins-ci-tidb/plugin-test	🟢 build success, plugin test success	4min	Existing passed