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_codegen_ssa/src/debuginfo/type_names.rs

@@ -585,7 +585,7 @@ fn coroutine_kind_label(coroutine_kind: Option<CoroutineKind>) -> &'static str {
         Some(CoroutineKind::Desugared(CoroutineDesugaring::AsyncGen, CoroutineSource::Fn)) => {
             "async_gen_fn"
         }
-        Some(CoroutineKind::Coroutine) => "coroutine",
+        Some(CoroutineKind::Coroutine(_)) => "coroutine",
         None => "closure",
     }
 }