hg-core: remove unneeded trait now that we support Rust 1.52+

rust: remove newly redundant `use` statements with the 2021 edition prelude https://doc.rust-lang.org/edition-guide/rust-2021/prelude.html

rust: move all crates in the main workspace to edition 2021 We've changed our minimum Rust version to 1.61.0 in the previous patch, and edition 2021 predates that version.

rust: upgrade supported Rust toolchain version A few months ago¹, a decision was made to move the Rust toolchain target to whatever Debian Testing was tracking. I didn't have the bandwidth to act on it until now. This is starting to be even more problematic than before, now that edition 2021 is out. The CI has been updated to track the current Debian testing version, 1.61.0. [1] https://lists.mercurial-scm.org/pipermail/mercurial-packaging/2022-April/000338.html

help: fix a py3 error interpolating Set into b'%s' I can't reproduce it, but a coworker hit this with `hg help -v` with 6.2.3: ... File "mercurial\help.pyc", line 865, in helplist TypeError: %b requires a bytes-like object, or an object that implements __bytes__, not 'set' I can confirm that the original expression fails in `hg debugshell`, and the new one works. The second instance was found by searching for "%s", but PyCharm detects a lot of variables as Any type, so I have no idea if there are other lurking problems.

branching: merge stable into default

Added signature for changeset c890d8b8bc59