[Diagnostics] Fix generic arguments mismatch diagnostic related to leading-dot syntax

`GenericArgumentsMismatchFailure` missed a case where location
of the failure points to a member spelled with leading-dot syntax.

Author: xedin

lib/Sema/CSDiagnostics.cpp

@@ -1037,7 +1037,8 @@ bool GenericArgumentsMismatchFailure::diagnoseAsError() {
       break;
     }
 
-    case ConstraintLocator::Member: {
+    case ConstraintLocator::Member:
+    case ConstraintLocator::UnresolvedMember: {
       auto *memberLoc = getConstraintLocator(anchor, path);
       auto selectedOverload = getOverloadChoiceIfAvailable(memberLoc);
       if (!selectedOverload)

test/Concurrency/sendable_to_any_for_generic_arguments.swift

@@ -175,3 +175,17 @@ func test_subscript_computed_property_and_mutating_access(u: User) {
 
   u.dict.testMutating() // Ok
 }
+
+extension Dictionary where Key == String, Value == Any {
+  init(age: Int) { // expected-note {{'init(age:)' declared here}}
+    self.init()
+  }
+}
+
+extension User {
+  convenience init(age: Int) {
+    self.init()
+    self.dict = .init(age: age)
+    // expected-error@-1 {{referencing initializer 'init(age:)' on '[String : any Sendable].Type' requires the types 'any Sendable' and 'Any' be equivalent}}
+  }
+}