tests/test-narrow-debugrebuilddirstate.t

tests: use simple mock smtp server instead of deprecated asyncore smtpd

test-patchbomb-tls.t would fail with:
  .../hg/tests/dummysmtpd.py:6: DeprecationWarning: The asyncore module is deprecated and will be removed in Python 3.12. The recommended replacement is asyncio
    import asyncore
  .../hg/tests/dummysmtpd.py:8: DeprecationWarning: The smtpd module is deprecated and unmaintained and will be removed in Python 3.12.  Please see aiosmtpd (https://aiosmtpd.readthedocs.io/) for the recommended replacement.
    import smtpd

The recommended migration path to the standalone asiosmtpd would be overkill.

The tests do not need a full smtp server - we can just use a very simple mock
hack to preserve the existing test coverage.

  $ . "$TESTDIR/narrow-library.sh"
  $ hg init master
  $ cd master
  $ echo treemanifest >> .hg/requires
  $ echo 'contents of file' > file
  $ mkdir foo
  $ echo 'contents of foo/bar' > foo/bar
  $ hg ci -Am 'some change'
  adding file
  adding foo/bar

  $ cd ..
  $ hg clone --narrow ssh://user@dummy/master copy --include=foo
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files
  new changesets * (glob)
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd copy

  $ hg debugdirstate --no-dates
  n *         20 *               foo/bar (glob)
  $ mv .hg/dirstate .hg/old_dirstate
  $ dd bs=40 count=1 if=.hg/old_dirstate of=.hg/dirstate 2>/dev/null
  $ hg debugdirstate
  $ hg debugrebuilddirstate
  $ hg debugdirstate
  n *         * unset               foo/bar (glob)