Auto merge of #79670 - Nadrieril:uninhabited-query, r=estebank

Turn type inhabitedness into a query to fix `exhaustive_patterns` perf

We measured in https://github.com/rust-lang/rust/pull/79394 that enabling the [`exhaustive_patterns` feature](https://github.com/rust-lang/rust/issues/51085) causes significant perf degradation. It was conjectured that the culprit is type inhabitedness checking, and [I hypothesized](https://github.com/rust-lang/rust/pull/79394#issuecomment-733861149) that turning this computation into a query would solve most of the problem.

This PR turns `tcx.is_ty_uninhabited_from` into a query, and I measured a 25% perf gain on the benchmark that stress-tests `exhaustiveness_patterns`. This more than compensates for the 30% perf hit I measured [when creating it](https://github.com/rust-lang/rustc-perf/pull/801). We'll have to measure enabling the feature again, but I suspect this fixes the perf regression entirely.
I'd like a perf run on this PR obviously.
I made small atomic commits to help reviewing. The first one is just me discovering the "revisions" feature of the testing framework.

I believe there's a push to move things out of `rustc_middle` because it's huge. I guess `inhabitedness/mod.rs` could be moved out, but it's quite small. `DefIdForest` might be movable somewhere too. I don't know what the policy is for that.

Ping `@camelid` since you were interested in following along
`@rustbot` modify labels: +A-exhaustiveness-checking

compiler/rustc_middle/src/ty/mod.rs

@@ -3155,6 +3155,7 @@ pub fn provide(providers: &mut ty::query::Providers) {
     *providers = ty::query::Providers {
         trait_impls_of: trait_def::trait_impls_of_provider,
         all_local_trait_impls: trait_def::all_local_trait_impls,
+        type_uninhabited_from: inhabitedness::type_uninhabited_from,
         ..*providers
     };
 }