Version: use git_identifier in vcs_url (#12459)
- This was duplicating the logic from git_identifier
- Our `latest` version already has the name of the branch/tag in the
identifier, no need to use `get_default_branch`
- We no longer create branches or tags with the origin prefix.
I'm doing small refactors to rely less on get_default_branch, as that
contains some extra logic that we already run to have `latest` always in
sync.
