Allow updating remote cache client certificates without rebooting

Background

Currently, the remote artifact cache reads in a single client certificate file and is unable to update this file without a reboot.

This works fine for a small team, especially if all members share a client certificate, but rebooting the server constantly to add client certificates is not going to work at scale.

Task description

We should modify the remote cache to allow loading and removing client certificates during run time.

Acceptance Criteria

The remote cache should no longer require reboots to manage client certificates.

---