Update code-ownership files to best utilize PROW + auto assign

[vMaroon]

Summary

• Use OWNERS and OWNERS_ALIASES for maintainer/reviewers maintenance + PROW permissions
• Use CODEOWNERS for automatic PR assignment. Note that PROW's blunderbuss was not used since it does not support granular assignment (e.g., guygir for the preprocessing package)

Once team management is more convenient in llm-d (cc @Gregory-Pereira perhaps?), teams can be synced with OWNERS_ALIASES for CODEOWNERS to also reference them.

[Copilot]

Pull Request Overview

This PR reorganizes code ownership and review assignment by introducing proper PROW-compatible ownership files and restructuring the CODEOWNERS file for automatic PR assignment.

• Introduces OWNERS_ALIASES to define maintainer and reviewer groups
• Updates OWNERS to use alias references instead of individual usernames
• Restructures CODEOWNERS to focus on automatic PR assignment with granular package-specific assignments

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
OWNERS_ALIASES	Defines maintainer and reviewer groups for PROW integration
OWNERS	Updates approvers and reviewers to reference alias groups
CODEOWNERS	Restructures for automatic PR assignment with clearer purpose
.licenserc.yaml	Adds OWNERS_ALIASES to license check exclusions

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[Copilot]

The maintainers group is listed in both approvers and reviewers sections. This creates redundancy since approvers typically have reviewer permissions by default. Consider removing the maintainers group from the reviewers list to avoid duplication.

Suggested change

	- llm-d-kv-cache-manager-maintainers
	- llm-d-kv-cache-manager-reviewers
	- llm-d-kv-cache-manager-reviewers

[vMaroon]

Unfortunately that is not true.

[nilig]

/lgtm

[nilig]

lgtm