[Serialization] Make a warning the diagnostic about attempting recovery

Use the `attempting forced recovery` diagnostic as main warning to which
we attach other messages as notes. Also mention the flag in the
diagnostic to reinforce that the flag is active.

Author: xymus

include/swift/AST/DiagnosticsSema.def

@@ -893,9 +893,9 @@ NOTE(modularization_issue_side_effect_type_error,none,
      "could not deserialize type for %0",
      (DeclName))
 
-NOTE(modularization_issue_worked_around,none,
-      "attempting forced recovery using top-level declaration from %0",
-      (Identifier))
+WARNING(modularization_issue_worked_around,none,
+        "attempting forced recovery enabled by -experimental-force-workaround-broken-modules",
+        ())
 
 ERROR(reserved_member_name,none,
       "type member must not be named %0, since it would conflict with the"

lib/Serialization/Deserialization.cpp

@@ -1962,13 +1962,12 @@ ModuleFile::resolveCrossReference(ModuleID MID, uint32_t pathLen) {
         errorKind == ModularizationError::Kind::DeclMoved &&
         !values.empty()) {
       // Print the error as a remark and notify of the recovery attempt.
+      getContext().Diags.diagnose(getSourceLoc(),
+                                  diag::modularization_issue_worked_around);
       llvm::handleAllErrors(std::move(error),
         [&](const ModularizationError &modularError) {
-          modularError.diagnose(this, DiagnosticBehavior::Remark);
+          modularError.diagnose(this, DiagnosticBehavior::Note);
         });
-      getContext().Diags.diagnose(getSourceLoc(),
-                                  diag::modularization_issue_worked_around,
-                                  foundIn);
     } else {
       return error;
     }

test/Serialization/modularization-error.swift

@@ -18,8 +18,8 @@
 // RUN: %target-swift-frontend -emit-sil %t/LibWithXRef.swiftmodule -module-name LibWithXRef -I %t \
 // RUN:   -experimental-force-workaround-broken-modules 2>&1 \
 // RUN:   | %FileCheck --check-prefixes CHECK-WORKAROUND %s
-// CHECK-WORKAROUND: remark: reference to type 'MyType' broken by a context change; 'MyType' was expected to be in 'A', but now a candidate is found only in 'B'
-// CHECK-WORKAROUND: note: attempting forced recovery using top-level declaration from 'B'
+// CHECK-WORKAROUND: warning: attempting forced recovery enabled by -experimental-force-workaround-broken-modules
+// CHECK-WORKAROUND: note: reference to type 'MyType' broken by a context change; 'MyType' was expected to be in 'A', but now a candidate is found only in 'B'
 // CHECK-WORKAROUND: func foo() -> some Proto
 
 /// Change MyType into a function.