Reject atomic distributed transaction on a network connection

[harshit-gangal]

Description

This PR rejects distributed transactions prepared when carried on a non-unix socket connection.

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

Deployment Notes

[codecov]

Codecov Report

Attention: Patch coverage is 47.36842% with 10 lines in your changes missing coverage. Please review.

Project coverage is 68.83%. Comparing base (61959f6) to head (3f0b9b8).
Report is 7 commits behind head on main.

Files	Patch %	Lines
go/vt/vttest/local_cluster.go	0.00%	7 Missing ⚠️
go/vt/vttablet/tabletserver/dt_executor.go	33.33%	2 Missing ⚠️
go/vt/vttablet/tabletserver/stateful_connection.go	75.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #16584      +/-   ##
==========================================
+ Coverage   68.77%   68.83%   +0.05%     
==========================================
  Files        1557     1557              
  Lines      199891   199949      +58     
==========================================
+ Hits       137483   137630     +147     
+ Misses      62408    62319      -89     

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[GuptaManan100]

Purrfect 🚀