scheduler: make ReservationInfo.AddAssignedPod idempotent

[eahydra]

Ⅰ. Describe what this PR does

When the scheduler starts, some Pods may be updated multiple times in a short period of time, causing the ReservationInfo to add the same Pod multiple times, and ultimately cannot be reused because the reservation's allocated is greater than or equal to the reservation's allocable.

The root cause is that the forceSyncEventHandler of the frameworkext helper module requires that all EventHandlers must be idempotent.

So the PR fix the issue. Make the ReservationInfo method AddAssignedPod idempotent.

Ⅱ. Does this pull request fix one issue?

Ⅲ. Describe how to verify it

Ⅳ. Special notes for reviews

V. Checklist

• I have written necessary docs and comments
• I have added necessary unit tests and integration tests
• All checks passed in make test

[codecov]

Codecov Report

Attention: 5 lines in your changes are missing coverage. Please review.

Comparison is base (58850b4) 65.91% compared to head (216effd) 65.90%.
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1709      +/-   ##
==========================================
- Coverage   65.91%   65.90%   -0.02%     
==========================================
  Files         384      384              
  Lines       41613    41628      +15     
==========================================
+ Hits        27430    27434       +4     
- Misses      12145    12157      +12     
+ Partials     2038     2037       -1     

Flag	Coverage Δ
unittests	65.90% <0.00%> (-0.02%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
...uler/frameworkext/helper/forcesync_eventhandler.go	77.33% <0.00%> (-1.05%)	⬇️
pkg/scheduler/frameworkext/reservation_info.go	30.00% <0.00%> (-0.59%)	⬇️

... and 9 files with indirect coverage changes

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[buptcozy]

/approve

[koordinator-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: buptcozy

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[buptcozy]

/lgtm