executor: use EncodeKey to encode groupkey in StreamAggExec (#49974)

[ti-chi-bot]

This is an automated cherry-pick of #49974

What problem does this PR solve?

Issue Number: close #49902

Problem Summary:

What changed and how does it work?

Use EncodeKey function to encode the groupkey within StreamAggExec. This approach is necessary as it considers collation when aggregating the result.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No need to test

  • I checked and no code files have been changed.

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.

Fixed the issue with StreamAgg that caused incorrect results due to mishandling collation ci.

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (release-7.5@bf303b5). Click here to learn what that means.
The diff coverage is n/a.

Additional details and impacted files

@@               Coverage Diff                @@
##             release-7.5     #50027   +/-   ##
================================================
  Coverage               ?   71.9687%           
================================================
  Files                  ?       1400           
  Lines                  ?     406585           
  Branches               ?          0           
================================================
  Hits                   ?     292614           
  Misses                 ?      94269           
  Partials               ?      19702           

Flag	Coverage Δ
unit	71.9687% <0.0000%> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
dumpling	53.9913% <0.0000%> (?)
parser	∅ <0.0000%> (?)
br	53.2832% <0.0000%> (?)

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: AilinKid, XuHuaiyu

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

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [AilinKid,XuHuaiyu]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-01-08 08:31:20.82923635 +0000 UTC m=+259270.413490037: ☑️ agreed by XuHuaiyu.
• 2024-01-08 08:50:34.736252104 +0000 UTC m=+260424.320505775: ☑️ agreed by AilinKid.