dirstate: use `reset_state` in `rebuild` instead of `dropfile`
As `dirstatemap.dropfile` is on its way out.
Differential Revision: https://phab.mercurial-scm.org/D11440
dirstate: use `reset_state` to drop file in `update_file_p1`
The `dropfile` function is on its way out.
Differential Revision: https://phab.mercurial-scm.org/D11439
dirstate: support file tracked nowhere in `reset_state`
This let the dirstatemap decide when to drop files.
Differential Revision: https://phab.mercurial-scm.org/D11438