### Godot version

3fa8fad

### System information

Debian Linux x86

### Issue description

#79205 introduces a regression to the way rpc configs are inherited, causing this error:

```
ERROR: Unable to get the RPC configuration for the function "foo" at path: "/root/Node". This happens when the method is missing or not marked for RPCs in the local script.
```

even though the function exists both in the server and the client. If you `print(self.foo)`, it even tells you that it's rpc: `Node(client.gd)::foo (rpc)` 

Before #79205 `GdScriptCompiler::_populate_class_members` used `GDScriptCache::get_full_script` to access the base script. This causes the parent script to be compiled (if it is not compiled yet), which in turn initializes the `rpc_config` property with a copy of the base value in [gdscript.cpp::_init_rpc_methods_properties](https://github.com/godotengine/godot/blob/3fa8fad26b97a8af20e7996b7e17d8f23fc04b89/modules/gdscript/gdscript.cpp#L1398-L1412)

However, `GDScriptCache::get_shallow_script` does not compile and thus does not initialize the `rpc_config` of the base script, causing the rpc functions not being included in the rpc config.

### Steps to reproduce

Extend a gdscript with a `@rpc` function annotation and try to do a network call:

server.gd:
```gdscript
extends Node

func _ready():
	var peer := ENetMultiplayerPeer.new()
	peer.create_server(1337)
	multiplayer.multiplayer_peer = peer

@rpc("any_peer") func foo():
	print("Server")
```

parent.gd:
```gdscript
extends Node

@rpc func foo(): pass
```

client.gd:
```gdscript
extends "parent.gd"

func _ready():
	var peer := ENetMultiplayerPeer.new()
	peer.create_client("localhost", 1337)
	multiplayer.connected_to_server.connect(func (): self.foo.rpc_id(1))
	multiplayer.multiplayer_peer = peer
```


### Minimal reproduction project

[test.zip](https://github.com/godotengine/godot/files/12215814/test.zip)

p_script->fully_qualified_name = p_class->fqcn;
	p_script->local_name = p_class->identifier ? p_class->identifier->name : StringName();
	p_script->global_name = p_class->get_global_name();
	p_script->simplified_icon_path = p_class->simplified_icon_path;
	HashMap<StringName, Ref<GDScript>> old_subclasses;
	if (p_keep_state) {
		old_subclasses = p_script->subclasses;
	}
	p_script->subclasses.clear();
	for (int i = 0; i < p_class->members.size(); i++) {
		if (p_class->members[i].type != GDScriptParser::ClassNode::Member::CLASS) {
			continue;
		}
		const GDScriptParser::ClassNode *inner_class = p_class->members[i].m_class;
		StringName name = inner_class->identifier->name;
		Ref<GDScript> subclass;
		if (old_subclasses.has(name)) {
			subclass = old_subclasses[name];
		} else {
			subclass = GDScriptLanguage::get_singleton()->get_orphan_subclass(inner_class->fqcn);
		}
		if (subclass.is_null()) {
			subclass.instantiate();
		}
		subclass->_owner = p_script;