feat: Implement Model Rewrite and Traffic Splitting Logic

[zetxqx]

What type of PR is this?

/kind feature

What this PR does / why we need it:

This pull request introduces the core logic for model rewriting and weighted traffic
splitting within the request control director. It also includes the reconciler logic for InferenceModelRewrite resources.

Key changes:

• pkg/epp/requestcontrol:
  • Adds the applyWeightedModelRewrite function to handle model rewriting based on
    InferenceModelRewrite rules.
  • Implements weighted selection of target models for traffic splitting.
  • Ensures that the oldest InferenceModelRewrite resource is respected in case of
    duplicate rules
• pkg/epp/controller:
  • Implements the read-only reconciler logic for InferenceModelRewrite resources

Which issue(s) this PR fixes:

Fixes partially #1811

Does this PR introduce a user-facing change?:

Users can now configure `InferenceModelRewrite` resources to automatically redirect 
incoming model requests to different target models. This feature also supports weighted 
traffic splitting, allowing you to distribute requests across multiple target models based
 on defined percentages.

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[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: zetxqx
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[zetxqx]

/retest