Make git pushing more resilient

[premun]

Context

When pushing codeflow branches at the end of an update, the push might fail for whatever reason:

• Transient problem
• Auth?
• Non-fast forward?

In those cases, the work item might fail and we never learn about it.
It would be nice if we started tracking the push event as a custom event / metric just like we do for git clone and other operations.
We could then alert when pushes fail and learn about those.

Goals

• Make pushing more resilient (at least a basic retry?) or make the work item retry when push fails for retriable reasons.
• Emit dedicated telemetry when pushing.
• Make sure we learn about the failures through Grafana alerts (similar to Handle failed code flow updates #4198).