Geo: Replace Git over HTTP calls with Workhorse HTTP endpoint for SSH pull

Contributes to #762 (closed)

Workhorse endpoint: Workhorse: HTTP endpoint for bidirectional SSH ... (gitlab!152950 - merged)

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.