[release-23.0] vtgate: set ServerStatusAutocommit in handshake status flags (#19628)

[vitess-bot]

Description

This is a backport of #19628

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.56%. Comparing base (550459d) to head (b91fdfb).
⚠️ Report is 6 commits behind head on release-23.0.

Additional details and impacted files

@@                Coverage Diff                @@
##           release-23.0   #19646       +/-   ##
=================================================
+ Coverage         69.45%   84.56%   +15.10%     
=================================================
  Files              1607      301     -1306     
  Lines            215090    54233   -160857     
=================================================
- Hits             149397    45860   -103537     
+ Misses            65693     8373    -57320     

Flag	Coverage Δ
partial	84.56% <100.00%> (?)

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