Proxy metric names for identity cert management are inaccurate for edge-24.5.1

After upgrading from linkerd2 `edge-24.3.5` to `edge-24.5.1` I've found that the following set of proxy metrics scraped from my pods have been renamed:

`identity_cert_refreshes_total` renamed to `control_identity_cert_refreshes_total`

`identity_cert_refresh_timestamp_seconds` renamed to `control_identity_cert_refresh_timestamp_seconds`

`identity_cert_expiration_timestamp_seconds` renamed to `control_identity_cert_expiration_timestamp_seconds`

I can't find the specific merge that introduced this change in prefix in the linkerd2-proxy or linkerd2 release notes, but if this was intentional the documentation will need to be updated to reflect this.

e.g. https://github.com/linkerd/website/blob/eb40950ca6b0999ea49dc49b9c238919657bbd3a/linkerd.io/content/2.15/reference/proxy-metrics.md?plain=1#L234

Start with linkerd.io/content/2.15/reference/proxy-metrics.md at the referenced section and compare its identity certificate metric names with the edge-24.5.1 names reported here. Check the linkerd2-proxy and Linkerd release notes for confirmation; done means the documentation accurately reflects the intentional metric names, or the discrepancy is clarified.

Written by the indexing model from the issue text.