Fail on prepare of reserved connection

[harshit-gangal]

Description

This PR reject distributed transaction prepare on reserved connection. These are the connection that are using temporary tables or locking feature. They are not safe to allow support for atomic commit.

Related Issue(s)

• RFC: Atomic Distributed Transactions #16245

Checklist

• 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

[vitess-bot]

Review Checklist

Hello reviewers! 👋 Please follow this checklist when reviewing this Pull Request.

General

• Ensure that the Pull Request has a descriptive title.
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Tests

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Backward compatibility

• Protobuf changes should be wire-compatible.
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• RPC changes should be compatible with vitess-operator
• If a flag is removed, then it should also be removed from vitess-operator and arewefastyet, if used there.
• vtctl command output order should be stable and awk-able.

[codecov]

Codecov Report

Attention: Patch coverage is 96.62921% with 3 lines in your changes missing coverage. Please review.

Project coverage is 68.71%. Comparing base (05d7e76) to head (22dea71).
Report is 2 commits behind head on main.

Files	Patch %	Lines
go/vt/vttablet/tabletserver/dt_executor.go	98.73%	1 Missing ⚠️
go/vt/vttablet/tabletserver/tabletserver.go	88.88%	1 Missing ⚠️
go/vt/vttablet/tabletserver/twopcz.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #16316      +/-   ##
==========================================
- Coverage   68.71%   68.71%   -0.01%     
==========================================
  Files        1547     1547              
  Lines      198260   198241      -19     
==========================================
- Hits       136238   136221      -17     
+ Misses      62022    62020       -2     

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[GuptaManan100]

LGTM