Investigate if Gitaly inherits ulimit settings

Context

In omnibus-gitlab#8209, several customers have experienced issues after upgrading their Omnibus GitLab installations where Gitaly couldn't serve requests as it was unable to spawn new processes. In all cases, the customer was able to resolve the problem by increasing the git user's process limit by modifying /etc/security/limits.conf.

In an Omnibus installation however, the runsv startup script already attempts to set shell process limits using ulimit. It's possible that either this isn't working or Gitaly isn't inheriting these new limits, but it's hard to tell due to a lack of logging.

Proposal

Investigate if these limits are being inherited by Gitaly processes correctly. Since the runsv script uses ulimit, these are only applied to processes forked from the current shell process, not universally in the system. The script hasn't changed in a number of years, so would've been in effect for all customers who reported problems in the issue.