Contributes to https://gitlab.com/gitlab-org/gitlab-shell/-/issues/762

**Problem**

There is a new endpoint for SSH Pull implemented in Workhorse. We
want to use it for Geo Git Pull calls.

**Solution**

* Define a boolean parameter `GeoProxyFetchSSHDirectToPrimary` hidden
behind the feature flag.
* Make a call to `ssh-upload-pack` endpoint for git pull commands.

Changelog: added

Change the usage of http.Client to retryablehttp.Client to take advantage
of the ability to retry queries and calls.

Ensure each of the function calls set their own headers.

Switch the hard-coded HTTP header string to be a constant given to each
of the Client objects.

Co-authored-by: Ash McKenzie <amckenzie@gitlab.com>

Fix capitalization of variables names
Change "cap" to capability to avoid built-in objects
Account for error responses in locks

Issue: https://gitlab.com/gitlab-org/gitlab/-/issues/336618

Issue: https://gitlab.com/gitlab-org/gitlab/-/issues/336618

Add a comment and the directive for the linter to ignore the fact that
one of our HTTP calls does not close.

Try to get ahead of future comments by running the lint test locally
and fixing issues that are found.

    * More variable capitalization issues
    * More unused variables -> "_"

* Replace variables with proper casing
* Use require.Len instead of requireEq with more parameters
* Pass the actual error code back in generated error.
* Move some unused variables to "_" until they are needed.

Issue: https://gitlab.com/gitlab-org/gitlab/-/issues/336618

Issue: https://gitlab.com/gitlab-org/gitlab/-/issues/336618