sparse: use the rust code even when sparse is present With rust supporting more matcher types, we can now take this route in the sparse case too.

sparse: directly inline the `set_tracked` and `copy` wrapping core is already aware of sparse, so lets move the handful of line of code that deal with this for the sake of simplicity and explicitness.

spares: clarify some test about merging copies This new output clarify the important part out this merging : we want to be able to record the copy source even it is outside of the sparse profile.

sparse: drop the useless wrapping of `dirstate.set_untracked` The code of the wrapper only act in the case where the file is not tracked, so this has not effect for `untracked`. In addition the message explicitly mention `add` of a file and no test are breaking if we drop this. So we drop this for simplicity and cleanup

sparse: directly inline the `rebuild` wrapping Core is already aware of sparse, so lets move the handful of line of code that deal with it in `dirstate.rebuild` for the sake of simplicity.

sparse: directly inline the `walk` wrapping core is already aware of sparse, so lets move the handful of line of code that deal with it in `dirstate.walk` for the sake of simplicity.

sparse: use None as the sparse matcher value when disabled This create a clear signal for when the feature is unused. We could also create an `alwaysmatcher`, but using None is more explicit, so I went for it.

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.