Frontend: Really allow any experimental feature when compiling a module interface.

The fix for https://github.com/apple/swift/pull/72632 was not sufficient
because when modules are built from textual interface that happens in a
sub-invocation which does not have typecheck-from-interface or
compile-from-interface requested action. Instead of checking a requested
action, set a language option to control whether non-production experimental
features are allowed.

Resolves rdar://125561443

lib/Frontend/ModuleInterfaceLoader.cpp

@@ -2066,6 +2066,12 @@ InterfaceSubContextDelegateImpl::runInSubCompilerInstance(StringRef moduleName,
   bool StrictImplicitModuleContext =
       subInvocation.getFrontendOptions().StrictImplicitModuleContext;
 
+  // It isn't appropriate to restrict use of experimental features in another
+  // module since it may have been built with a different compiler that allowed
+  // the use of the feature.
+  subInvocation.getLangOptions().RestrictNonProductionExperimentalFeatures =
+      false;
+
   // Save the target triple from the original context.
   llvm::Triple originalTargetTriple(subInvocation.getLangOptions().Target);