[feat: aga] add basic framework for AGA controller

[shraddhabang]

Acknowledge-by and Initial POC done by: Taylor Smith [taylorsmithgg]
#4314

Issue

Fixes #1572

Description

• New Controller: Added globalaccelerator_controller.go with basic framework of reconciliation logic, finalizer management, and error handling. Follows established controller patterns.

• Configuration: Added controller-specific config options and feature gate support

• Metrics: Integrated AGA-specific metrics collection and reconcile tracking

• Events: Added GlobalAccelerator event reasons for operational visibility

• RBAC: Updated permissions for GlobalAccelerator resources in both Kubernetes manifests and Helm charts

• Integration: Registered controller with manager and added proper scheme registration

Testing

1. Tested that the controller is getting events for AGA creation and deletions.
2. Feature gate is working as expected

Checklist

• Added tests that cover your change (if possible)
• Added/modified documentation as required (such as the README.md, or the docs directory)
• Manually tested
• Made sure the title of the PR is a good description that can go into the release notes

BONUS POINTS checklist: complete for good vibes and maybe prizes?! 🤯

• Backfilled missing tests for code in same general area 🎉
• Refactored something and made the world a better place 🌟

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: shraddhabang, zac-nixon

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[shuqz]

/lgtm