test: explicitly "add" file before some commit in test-rollback.t `hg commit -A` will revert the `hg addremove` step if the commit fails. However `hg rollback` currently does not. We are about to improve internal consistency around transaction and dirstate and the behavior of `hg rollback` will align on the other behavior in the process. Before doing so, we make sure the test is using a separate call to `hg add` to avoid the test scenario to be affected by that future change. note: the behavior change for `hg rollback` seems fine as it affect a niche usecase and `hg rollback` usage have been strongly discouraged for a while.

rhg-files: add support for narrow when specifying a revision This makes it so that `rhg files -r NODE` works properly when using narrow.

rust-narrow: enable narrow support for plain `rhg files` Support for `rhg files -r NODE` in a future changeset.

rhg-files: make signature of `display_files` more flexible This allows the callers to use any error type that converts to `CommandError` instead of a particular concrete type.

rhg: fix user-facing error message so it matches Python implementation

rust-ui: refactor ui code for printing narrow/sparse warnings This will be used elsewhere in the code, starting from the next commit.

rhg-files: reuse centralized dirstate logic The `files` logic predates the centralized dirstate logic. It was duplicated, an didn't receive bugfixes along the way.

rust: move `filter_map_results` to public util This is a useful general-purpose function. It will be used in the next changesets.

rhg: fix typo

run-tests: stop ignoring venv-installed packages This will allow test dependencies to be installed within a venv, instead of tampering with sys/user sites. One thing to note here is that the `VIRTUAL_ENV` path takes precedence over system-site, unlike when run directly with an activated `venv`. For example, `sys.path` as viewed from a feature test in `hghave.py`, when running `hghave vcr` directly with an activated `venv`: sys.path: [ '/home/jenkins/hg-committed/tests', '/usr/lib/python38.zip', '/usr/lib/python3.8', '/usr/lib/python3.8/lib-dynload', '/home/jenkins/test_venv/lib/python3.8/site-packages' ] vs `sys.path` from the same feature test, when run by `run-tests.py` with this change: sys.path: [ '/home/jenkins/hg-committed/tests', '/home/jenkins/hg-committed', '/home/jenkins/hg-committed/tests', '/home/jenkins/test_venv/lib/python3.8/site-packages', '/usr/lib/python38.zip', '/usr/lib/python3.8', '/usr/lib/python3.8/lib-dynload', '/home/jenkins/.local/lib/python3.8/site-packages', '/usr/local/lib/python3.8/dist-packages', '/usr/lib/python3/dist-packages' ]