[darc/maestro++] Maestro should synchronize version update branch when pushing new updates

When pushing new updates to a PR, Maestro/DarcLib should update the PR branch with the target branch (if possible). While GitHub/AzDO will do this when creating the merge branch, if a user has to make modifications on top of the PR branch, they will likely download and modify an out of date branch. Typically this would happen when an update causes a failure which sits for a few days.