localrepo: remove _readrequires function in favor of scmutil.readrequires

scmutil: add `readrequires` next to `writerequires` The code is copied from localrepo.py.

typing: correct a type hint in `mercurial.manifest` Obvious typo that was flagged by PyCharm.

typing: add hints to `mercurial.util.mktempcopy()` Might as well, now that the previous commit indicated what types are required.

typing: fix the hint for the `mode` argument of `platform.copymode()` The posix module is doing a bitwise AND with this and an integer, so it can't be bytes. The only caller that provides the argument is `util.mktempcopy()`, and pytype infers the type as Any, which explains why this wasn't caught.

largefiles: fix check that ensures that --all-largefiles is only used locally Previously, the command added in the test failed with “abort: --all-largefiles is incompatible with non-local destination existing_destination”. The reason for the buggy behavior was the use of hg.islocal(), which does “return true if repo (or path pointing to repo) is local” and, for local paths, assumes that the path is actually pointing to an existing repository and returns whether the path is not a regular file (in which case it assumes that it is a bundlerepo, which are considered non-local).

exchange: trivial simplification Both sides of the condition do essentially the same thing, except one with fastpath=True. No functional changes.

import: fix erroneous comparison of str with bytes