Add Priority and PreemptionPolicy fields in ResourceBinding

[seanlaii]

What type of PR is this?
/kind api-change
/kind feature

What this PR does / why we need it:
Add Priority and PreemptionPolicy fields in ResourceBinding to support priority-based scheduling. This enables:

• Priority-based scheduling for ResourceBindings
• Preemption control through PreemptionPolicy
• Better control over scheduling order of workloads across clusters

Which issue(s) this PR fixes:
Part of #5961

Special notes for your reviewer:

• Priority field is added as int32 to align with Kubernetes conventions
• PreemptionPolicy supports two modes: Never (default) and PreemptLowerPriority

Does this PR introduce a user-facing change?:

Add Priority and PreemptionPolicy fields to ResourceBinding API to support priority-based scheduling and preemption control.
- Priority: Defines scheduling priority (higher values = higher priority)
- PreemptionPolicy: Controls whether binding can preempt lower priority bindings

[karmada-bot]

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[seanlaii]

Since we don't allow the user to override the priority in the binding, and the priority value can only be derived by the priority class, I use int32 instead of *int32 for now. Open to discussion.

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Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 48.17%. Comparing base (8d89d77) to head (9ceb28b).

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Additional details and impacted files

@@           Coverage Diff           @@
##           master    #5963   +/-   ##
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  Coverage   48.17%   48.17%           
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  Files         664      664           
  Lines       54799    54799           
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+ Hits        26399    26400    +1     
  Misses      26684    26684           
+ Partials     1716     1715    -1     

Flag	Coverage Δ
unittests	48.17% <ø> (+<0.01%)	⬆️

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