Add admin_limit to cc.rate_limiter configuration

[WeiQuan0605]

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• A short explanation of the proposed change:
  CF API rate limits currently exclude admin users entirely. This PR extends cc.rate_limiter with an admin_limit parameter (default -1 = no limit, preserving existing behavior) that when set to a positive value applies rate limiting to admin users using their own counter, independent of the general user limit.

• An explanation of the use cases your change solves

  • Operators want to protect the CF API from abusive or runaway automation scripts running with admin credentials
  • Without this change, admin users can send unlimited requests and potentially overwhelm the API, while regular users are protected
  • With admin_limit: -1 (default), existing deployments are unaffected

• Links to any other associated PRs
  Capi-release Add admin_limit to cc.rate_limiter configuration capi-release#655

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• I have viewed, signed, and submitted the Contributor License Agreement

• I have made this pull request to the main branch

• I have run all the unit tests using bundle exec rake

• I have run CF Acceptance Tests