manifests: push down expected node length into the parser This strictly enforces the node length in the manifest lines according to what the repository expects. One test case moves large hash testing into the non-treemanifest part as treemanifests don't provide an interface for overriding just the node length for now. Differential Revision: https://phab.mercurial-scm.org/D10533

  $ rm -rf a
  $ hg init a
  $ cd a
  $ echo a > a
  $ hg ci -Am0
  adding a
  $ hg tag t1 # 1
  $ hg tag --remove t1 # 2

  $ hg co 1
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg tag -f -r0 t1
  $ hg tags
  tip                                3:a49829c4fc11
  t1                                 0:f7b1eb17ad24

  $ cd ..