remove: grpc-send-session-in-streaming flag

[anujagrawal380]

Description

Removes the deprecated --grpc-send-session-in-streaming VTGate flag, as tracked in #17913.

This flag was deprecated in v22 #17907 with a default of true. The session is now unconditionally sent as the last packet in StreamExecute and StreamExecuteMulti gRPC responses.

Changes

• Removed sendSessionInStreaming variable and flag registration from grpcvtgateservice/server.go
• Made session-sending behavior unconditional in both streaming RPCs
• Added changelog entry for v24.0.0

Related Issue(s)

Fixes #17913

Checklist

• "Backport to:" labels have been added if this change should be back-ported to release branches
• If this change is to be back-ported to previous releases, a justification is included in the PR description
• Tests were added or are not required
• Did the new or modified tests pass consistently locally and on CI?
• Documentation was added or is not required

Deployment Notes

AI Disclosure

Change log updated by Claude

[vitess-bot]

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[codecov]

Codecov Report

❌ Patch coverage is 80.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 69.66%. Comparing base (70c7a72) to head (111f80e).
⚠️ Report is 27 commits behind head on main.

Files with missing lines	Patch %	Lines
go/vt/vtgate/grpcvtgateservice/server.go	80.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #19443      +/-   ##
==========================================
- Coverage   69.67%   69.66%   -0.02%     
==========================================
  Files        1614     1614              
  Lines      216793   216815      +22     
==========================================
- Hits       151044   151034      -10     
- Misses      65749    65781      +32     

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[anujagrawal380]

PTAL @harshit-gangal @mattlord

[mhamza15]

@anujagrawal380 Thanks for the contribution! Please update the description following the PR template, and for future PRs try to follow it as well. Thanks!