tests/test-empty.t

dirstate: remove need_delay logic

Now that all¹ stored mtime are non ambiguous, we no longer need to apply the `need_delay` step.
The need delay logic was not great are mtime gathered during longer operation
could be ambiguous but younger than the `dirstate.write` call time.

So, we don't need that logic anymore and can drop it

This make the code much simpler. The code related to the test extension faking
the dirstate write is now obsolete and associated test will be migrated as
follow up. They currently do not break.

[1] except the ones from `hg update`, but `need_delay` no longer help for them
either.

Differential Revision: https://phab.mercurial-scm.org/D11796

Create an empty repo:

  $ hg init a
  $ cd a

Try some commands:

  $ hg log
  $ hg grep wah
  [1]
  $ hg manifest
  $ hg verify
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  checked 0 changesets with 0 changes to 0 files

Check the basic files created:

  $ ls .hg
  00changelog.i
  cache
  requires
  store
  wcache

Should be empty:

  $ ls .hg/store

Poke at a clone:

  $ cd ..
  $ hg clone a b
  updating to branch default
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd b
  $ hg verify
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  checked 0 changesets with 0 changes to 0 files
  $ ls .hg
  00changelog.i
  cache
  dirstate
  hgrc
  requires
  store
  wcache

Should be empty:

  $ ls .hg/store

  $ cd ..