### 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)

if (is_root_script()) {
		Script::set_path(p_path, p_take_over);
	}
	String old_path = path;
	path = p_path;
	GDScriptCache::move_script(old_path, p_path);
	for (KeyValue<StringName, Ref<GDScript>> &kv : subclasses) {
		kv.value->set_path(p_path, p_take_over);
	}
}
String GDScript::get_script_path() const {
	return path;
}
Error GDScript::load_source_code(const String &p_path) {
	if (p_path.is_empty() || p_path.begins_with("gdscript://") || ResourceLoader::get_resource_type(p_path.get_slice("::", 0)) == "PackedScene") {
		return OK;
	}
	Vector<uint8_t> sourcef;
	Error err;
	Ref<FileAccess> f = FileAccess::open(p_path, FileAccess::READ, &err);
	if (err) {
		const char *err_name;
		if (err < 0 || err >= ERR_MAX) {
			err_name = "(invalid error code)";
		} else {
			err_name = error_names[err];
		}
		ERR_FAIL_COND_V_MSG(err, err, "Attempt to open script '" + p_path + "' resulted in error '" + err_name + "'.");
	}
	uint64_t len = f->get_length();