Save some time on some tests using synctest

[mhamza15]

Description

Saving some time on some slow tests using synctest. Slow tests pulled from changes in #19076.

Before:

--- PASS: TestSleepTablet (15.01s)
    --- PASS: TestSleepTablet/default_sleep_duration (15.00s)
--- PASS: TestEmergencyReparentShardSlow (0.00s)
    --- PASS: TestEmergencyReparentShardSlow/nil_WaitReplicasTimeout_and_request_takes_29_seconds_is_ok (29.00s)
    --- PASS: TestEmergencyReparentShardSlow/nil_WaitReplicasTimeout_and_request_takes_31_seconds_is_error (30.00s)
--- PASS: TestPlannedReparentShardSlow (0.00s)
    --- PASS: TestPlannedReparentShardSlow/nil_WaitReplicasTimeout_and_request_takes_29_seconds_is_ok (28.01s)
    --- PASS: TestPlannedReparentShardSlow/nil_WaitReplicasTimeout_and_request_takes_31_seconds_is_error (30.00s)
ok  	vitess.io/vitess/go/vt/vtctl/grpcvtctldserver	30.854s

After:

--- PASS: TestSleepTablet (0.00s)
    --- PASS: TestSleepTablet/default_sleep_duration (0.00s)
--- PASS: TestEmergencyReparentShardSlow (0.00s)
    --- PASS: TestEmergencyReparentShardSlow/nil_WaitReplicasTimeout_and_request_takes_29_seconds_is_ok (0.01s)
    --- PASS: TestEmergencyReparentShardSlow/nil_WaitReplicasTimeout_and_request_takes_31_seconds_is_error (0.00s)
--- PASS: TestPlannedReparentShardSlow (0.00s)
    --- PASS: TestPlannedReparentShardSlow/nil_WaitReplicasTimeout_and_request_takes_29_seconds_is_ok (0.01s)
    --- PASS: TestPlannedReparentShardSlow/nil_WaitReplicasTimeout_and_request_takes_31_seconds_is_error (0.01s)
ok  	vitess.io/vitess/go/vt/vtctl/grpcvtctldserver	0.880s

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]

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 69.90%. Comparing base (32b8bd8) to head (86d0ddc).
⚠️ Report is 5 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #19112   +/-   ##
=======================================
  Coverage   69.89%   69.90%           
=======================================
  Files        1612     1612           
  Lines      215826   215826           
=======================================
+ Hits       150857   150863    +6     
+ Misses      64969    64963    -6     

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[arthurschreiber]

Nice! I made a similar attempt to speed up other test cases here: #18701

My main concern is around back ports. Synctest was added in go 1.25, but on v22 we are still using go 1.24 so adding this in too many places will potentially make back ports a bit more complicated. But I think there's going to be a lot of test cases where the improvement is so significant that we can still make this trade off. 👍

[mattlord]

❤️