Add benchmark committee members

[mhmdk0]

Adds benchmark committee members: owners can assign other users as committee members who receive the same management permissions for that benchmark.

• Server: committee_members M2M on Benchmark, committee_member_emails on read/write API, IsCommitteeMember on benchmark and association endpoints.
• CLI: medperf benchmark update_committee_members -b --committee_emails_file (same pattern as update_associations_policy)
• Web UI: committee member email editor on the benchmark detail page

[github-actions]

MLCommons CLA bot All contributors have signed the MLCommons CLA ✍️ ✅