Auto merge of #112001 - saethlin:enable-matchbranchsimplification, r=cjgillot

Enable MatchBranchSimplification

This pass is one of the small number of benefits from `-Zmir-opt-level=3` that has motivated rustc_codegen_cranelift to use it:

19ed0aade6/compiler/rustc_codegen_cranelift/build_system/build_sysroot.rs (L244-L246)

Cranelift's motivation for this is _runtime_ performance improvements in debug builds. Lifting this pass all the way to `-Zmir-opt-level=1` seems to come without significant perf overhead, so that's what I'm suggesting here.

compiler/rustc_trait_selection/src/traits/fulfill.rs

@@ -116,6 +116,7 @@ impl<'a, 'tcx> FulfillmentContext<'tcx> {
 }
 
 impl<'tcx> TraitEngine<'tcx> for FulfillmentContext<'tcx> {
+    #[inline]
     fn register_predicate_obligation(
         &mut self,
         infcx: &InferCtxt<'tcx>,