VReplication: Improve error handling in VTGate VStreams

[mattlord]

Description

This PR improves the error handling for VTGate VStreams by adding additional context to the error whenever we can. The issue (#17548) mentioned lower level MySQL errors that were previously addressed in #12095 but this PR goes over the full path and makes some minor but nice improvements.

Related Issue(s)

• Fixes: Feature Request: Improve VStream Error Messages #17548
• Follow-up to: VReplication: Propagate Binlog Stream Errors #12095

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

[vitess-bot]

Review Checklist

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[codecov]

Codecov Report

Attention: Patch coverage is 32.55814% with 58 lines in your changes missing coverage. Please review.

Project coverage is 67.80%. Comparing base (71b2cae) to head (bc558bf).
Report is 20 commits behind head on main.

Files with missing lines	Patch %	Lines
go/vt/vtgate/vstream_manager.go	43.33%	34 Missing ⚠️
go/vt/vttablet/tabletserver/vstreamer/vstreamer.go	7.69%	24 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #17558      +/-   ##
==========================================
+ Coverage   67.77%   67.80%   +0.02%     
==========================================
  Files        1587     1587              
  Lines      255798   255854      +56     
==========================================
+ Hits       173379   173474      +95     
+ Misses      82419    82380      -39     

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