Support TLS connections for all metrics endpoints in GitLab components

This might be better as a sub-epic of FIPS compliance, with an issue per project that needs modifications.

GitLab components report metrics via Prometheus, and sometimes start a pprof listener to aid live profiling. Either of these may be open and listening when running GitLab in production, as they are on GitLab.com

Here's a list of ones I've spotted so far. It's probably not comprehensive:

• gitlab-workhorse
• gitlab-rails
• gitlab-sshd
• gitlab-pages

Currently, none of these endpoints are capable of being TLS-secured. In a FIPS-compliant setup, I think we must TLS-secure them all. This implies taking a key+cert in addition to the listen address.

We also need to get https://github.com/prometheus/common/pull/283 merged, as prometheus uses MD5 internally for one thing.