scheduler: support reserving pods resources

[saintube]

Ⅰ. Describe what this PR does

Reservation supports reserving "pods" resources. It helps when we want to limit the allocatable "pods" of the reservation owners.

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: Patch coverage is 81.81818% with 4 lines in your changes missing coverage. Please review.

Project coverage is 67.33%. Comparing base (2fde51c) to head (34cde91).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/scheduler/frameworkext/reservation_info.go	0.00%	2 Missing ⚠️
pkg/scheduler/plugins/reservation/transformer.go	33.33%	0 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2224      +/-   ##
==========================================
+ Coverage   67.29%   67.33%   +0.03%     
==========================================
  Files         453      453              
  Lines       43687    43703      +16     
==========================================
+ Hits        29401    29427      +26     
+ Misses      11740    11731       -9     
+ Partials     2546     2545       -1     

Flag	Coverage Δ
unittests	67.33% <81.81%> (+0.03%)	⬆️

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[zwzhang0107]

/lgtm
/approve