scheduler: some minor optimizations for reservation

[saintube]

Ⅰ. Describe what this PR does

Scheduler: Reduce overhead by changing unnecessary DeepCopy to shallow copy and pre-allocating memory for a heavy map copy.

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 57.14286% with 3 lines in your changes missing coverage. Please review.

Project coverage is 65.90%. Comparing base (04292dc) to head (627e5e5).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/scheduler/frameworkext/reservation_info.go	0.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2336      +/-   ##
==========================================
- Coverage   65.92%   65.90%   -0.02%     
==========================================
  Files         466      466              
  Lines       54811    54812       +1     
==========================================
- Hits        36134    36125       -9     
- Misses      16067    16076       +9     
- Partials     2610     2611       +1     

Flag	Coverage Δ
unittests	65.90% <57.14%> (-0.02%)	⬇️

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