LibJS+LibWeb: Another round of bringing module loading closer to spec

In particular, this patch focuses on:
- Updating the old "import assertions" to the new "import attributes"
- Allowing realms as module import referrer

Userland/Libraries/LibJS/Forward.h

@@ -162,6 +162,7 @@ class ClassExpression;
 struct ClassFieldDefinition;
 class Completion;
 class Console;
+class CyclicModule;
 class DeclarativeEnvironment;
 class DeferGC;
 class ECMAScriptFunctionObject;
@@ -178,6 +179,7 @@ class FunctionNode;
 struct FunctionParameter;
 class GlobalEnvironment;
 class GlobalObject;
+struct GraphLoadingState;
 class HandleImpl;
 class Heap;
 class HeapBlock;