operations: Convert test hooks to use Bash instead of Ruby

As we're progressing with out conversion of Ruby-based code we're drawing ever closer to a future where there is no Ruby in Gitaly's code base anymore. Some of our tests still depend on Ruby though because they use a set of custom hooks that are implemented in it.

Refactor these scripts to use Bash instead of Ruby. This requires less boilerplate code and gets rid of the last set of custom hooks in our tests that use Ruby.