Add semi-sync plugin test in main

[GuptaManan100]

Description

This PR adds the test that were added to release-20 in #16357 to main as well. The tests have their expectations changed slightly given that they are running on main where the default semi-sync plugin is going to be of SOURCE type instead of MASTER

Related Issue(s)

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

[vitess-bot]

Review Checklist

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 68.67%. Comparing base (0f242e9) to head (47b7fba).

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #16372      +/-   ##
==========================================
- Coverage   68.67%   68.67%   -0.01%     
==========================================
  Files        1548     1548              
  Lines      199083   199083              
==========================================
- Hits       136727   136716      -11     
- Misses      62356    62367      +11     

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