[Feature Flag] Create enable_hamilton_in_usage_quotas_ui

What does this MR do and why?

Relates to https://gitlab.com/gitlab-org/gitlab/-/issues/411850 – this MR:

• introduces the enable_hamilton_in_usage_quotas_ui Feature Flag and
• pushes it to the Usage Quotas controller

Screenshots or screen recordings

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How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

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• I have evaluated the MR acceptance checklist for this MR.