pep-517: remove the `build-backend` key to allow for users to build extensions PEP 517 changed how projects should define their build dependencies. The presence of a `pyproject.toml` file changes the behavior of `pip` to conform to PEP 517. Since we haven't updated the `setup.py` file yet (I'm not even sure we're not an edge case which would make it harder/impossible, I have not tried yet), this is a workaround to issue6589: it allows users to pass `--no-use-pep517` to pip to revert to the legacy installer. The build backend is simply assumed to be the `build_meta:__legacy__` one. Differential Revision: https://phab.mercurial-scm.org/D11393

dirstate: drop the `dirstatemap.dropfile` method All use have been migrated. Differential Revision: https://phab.mercurial-scm.org/D11443

dirstate: use `reset_state` instead of `dropfile` in test-rebuildstate.t As `dirstatemap.dropfile` is on its way out. Differential Revision: https://phab.mercurial-scm.org/D11442

dirstate: use `reset_state` instead of `dropfile` in largefile As `dirstatemap.dropfile` is on its way out. Differential Revision: https://phab.mercurial-scm.org/D11441

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

dirstate: drop dirstatemap.addfile All users have been migrated. Differential Revision: https://phab.mercurial-scm.org/D11437

dirstate: update the documentation of the dirstatemap API The API changed so should the documentation. Differential Revision: https://phab.mercurial-scm.org/D11436

dirstate: drop the `_addpath` method All user have been migrated. Differential Revision: https://phab.mercurial-scm.org/D11435