branchcache: add more test for the logic around obsolescence and branch heads While working on branch-cache-v3, we noticed some ambiguity in the filtered+obsolete hash. However this was only caught by a rebase test by chance. It seems important to explicitly tests these cases.

  $ LANG=nonexistent LC_ALL=nonexistent LANGUAGE=nonexistent hg version -q
  Mercurial Distributed SCM (version *) (glob)