Auto merge of #107507 - BoxyUwU:deferred_projection_equality, r=lcnr

Implement `deferred_projection_equality` for erica solver

Somewhat of a revival of #96912. When relating projections now emit an `AliasEq` obligation instead of attempting to determine equality of projections that may not be as normalized as possible (i.e. because of lazy norm, or just containing inference variables that prevent us from resolving an impl). Only do this when the new solver is enabled

compiler/rustc_hir_analysis/src/astconv/mod.rs

@@ -1320,6 +1320,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                     ty::Clause::RegionOutlives(_) => bug!(),
                 },
                 ty::PredicateKind::WellFormed(_)
+                | ty::PredicateKind::AliasEq(..)
                 | ty::PredicateKind::ObjectSafe(_)
                 | ty::PredicateKind::ClosureKind(_, _, _)
                 | ty::PredicateKind::Subtype(_)