test: showcase using synctest

[arthurschreiber]

Description

synctest is a new builtin go package that was marked as stable in 1.25. It allows execution of time based test (e.g. those that test timeouts via context etc) without actually spending time waiting for the given timeout to fire.

See the documentation at https://pkg.go.dev/testing/synctest and Testing concurrent code with testing/synctest for more information on how this works. Using this package for unit tests is pretty straightforward and painless, and has huge potential to improve test runtimes.

In this PR, I'm updating the vstream manager unit tests that effectively test passing time. Just wrapping these tests in synctest.Test yields a test execution time reduction of 97.5%.

Before

ok  	vitess.io/vitess/go/vt/vtgate	47.349s

After

ok  	vitess.io/vitess/go/vt/vtgate	1.171s

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

AI Disclosure

[vitess-bot]

Review Checklist

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General

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

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 67.50%. Comparing base (be0c44f) to head (39705b4).
⚠️ Report is 69 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #18701      +/-   ##
==========================================
- Coverage   67.51%   67.50%   -0.02%     
==========================================
  Files        1608     1608              
  Lines      263594   263604      +10     
==========================================
- Hits       177973   177947      -26     
- Misses      85621    85657      +36     

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[github-actions]

This PR is being marked as stale because it has been open for 30 days with no activity. To rectify, you may do any of the following:

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If no action is taken within 7 days, this PR will be closed.