When converting an expression to type type, retain the resulting instruction as well as the TypeId. (#4355)

The `TypeId` is lossy, as it represents only the canonical type, and not
the specific computation that produced it.

toolchain/check/handle_array.cpp

@@ -49,7 +49,8 @@ auto HandleParseNode(Context& context, Parse::ArrayExprId node_id) -> bool {
       node_id, {.type_id = SemIR::TypeId::TypeType,
                 .bound_id = bound_inst_id,
                 .element_type_id = ExprAsType(context, element_type_node_id,
-                                              element_type_inst_id)});
+                                              element_type_inst_id)
+                                       .type_id});
   return true;
 }