Auto merge of #119258 - compiler-errors:closure-kind, r=eholk

Make closures carry their own ClosureKind

Right now, we use the "`movability`" field of `hir::Closure` to distinguish a closure and a coroutine. This is paired together with the `CoroutineKind`, which is located not in the `hir::Closure`, but the `hir::Body`. This is strange and redundant.

This PR introduces `ClosureKind` with two variants -- `Closure` and `Coroutine`, which is put into `hir::Closure`. The `CoroutineKind` is thus removed from `hir::Body`, and `Option<Movability>` no longer needs to be a stand-in for "is this a closure or a coroutine".

r? eholk

compiler/rustc_hir_analysis/src/check/region.rs

@@ -824,10 +824,6 @@ impl<'tcx> Visitor<'tcx> for RegionResolutionVisitor<'tcx> {
             resolve_local(self, None, Some(body.value));
         }
 
-        if body.coroutine_kind.is_some() {
-            self.scope_tree.body_expr_count.insert(body_id, self.expr_and_pat_count);
-        }
-
         // Restore context we had at the start.
         self.expr_and_pat_count = outer_ec;
         self.cx = outer_cx;