dirstatemap: rename `_rustmap` to `_map`
This match the name of the `map` for the other implementation and will make it
simpler to share code between the two.
Differential Revision: https://phab.mercurial-scm.org/D11566
#require clang-format test-repo
$ . "$TESTDIR/helpers-testrepo.sh"
$ cd "$TESTDIR"/..
$ for f in `testrepohg files 'set:(**.c or **.cc or **.h) and not "listfile:contrib/clang-format-ignorelist"'` ; do
> clang-format --style file $f > $f.formatted
> cmp $f $f.formatted || diff -u $f $f.formatted
> rm $f.formatted
> done