Downgrade more sendability errors involving metatypes to warnings

(cherry picked from commit c7c152b)

Author: DougGregor

lib/Sema/TypeCheckConcurrency.cpp

@@ -6731,8 +6731,7 @@ static bool checkSendableInstanceStorage(
           elementType, context,
           /*inDerivedConformance*/Type(), element->getLoc(),
           [&](Type type, DiagnosticBehavior behavior) {
-            auto preconcurrency =
-                context.preconcurrencyBehavior(type->getAnyNominal());
+            auto preconcurrency = context.preconcurrencyBehavior(type);
             if (isImplicitSendableCheck(check)) {
               // If this is for an externally-visible conformance, fail.
               if (check == SendableCheck::ImplicitForExternallyVisible) {

test/Concurrency/sendable_metatype_typecheck.swift

@@ -117,3 +117,11 @@ class Holder: @unchecked Sendable {
     2: String.self,
   ]
 }
+
+enum E: Sendable {
+case q(Q.Type, Int) // expected-warning{{associated value 'q' of 'Sendable'-conforming enum 'E' has non-sendable type 'any Q.Type'}}
+}
+
+struct S: Sendable {
+  var tuple: ([Q.Type], Int) // expected-warning{{stored property 'tuple' of 'Sendable'-conforming struct 'S' has non-sendable type '([any Q.Type], Int)'}}
+}