sparse: start moving away from the global variable for detection of usage Code is now checking if the repository using the sparse feature and that's it. Some code in `debugsparse` still rely on "global" state, as it apply sparse logic before updating the requirement. Cleaning that up is more work that we signed up for, but we could narrow the hack to that specific command.

test: fix test-sparse-revlog output after debugdeltachain change We need to get this test covered by the CI, in the meantime, here is a quick fix.

rust-dirstate: add support for nevermatcher This is in case this ever comes up, it's very easy to support, so might as well do it.

rust-dirstate: add `intersectionmatcher` to the allowed matchers `IntersectionMatcher` is now implemented in Rust.

rust: add IntersectionMatcher This will be used in the upcoming support for sparse checkouts in Rust-augmented status and later in rhg support for sparse checkouts.

rust-dirstate: add `unionmatcher` to the allowed matchers `UnionMatcher` is now implemented in Rust.

rust: add UnionMatcher This will be used in the upcoming support for sparse checkouts in Rust-augmented status and later in rhg support for sparse checkouts.

hg-cpython: refactor matcher transformation logic This reduces duplication and will allow for recursive transformation in UnionMatcher.

rust: use owned types in `Matcher` This simplifies the code a lot, allows for some refactoring to come. The original code tried to prevent allocations that were already happening anyway beforehand.

hg-cpython: fallback when encountering an unknown matcher At this point in the process, nothing user-visible has happened, it is still safe to fallback. This can happen now that we're going to be using "container matchers" like unionmatcher and intersectionmatcher. This is easier and less error-prone than recursive checking beforehand since only the presence of a transformation case will allow the process to continue.