Brightness control doesn't work with mutter-49+

### What Happened?

Since gnome 49 gnome-settings-daemon's dbus interface for managing backlight was removed. If I understood correctly, now gnome-shell directly "asks" mutter to change it using new `Meta.Backlight` class. Perhaps gala can implement its own dbus interface for managing screen brightness?

Relevant MRs:
https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/4014
https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/3715

### Steps to Reproduce

1. Try to change brightness when running gala with mutter 49+
2. Nothing happens

### Expected Behavior

Screen brightness changing

### OS Version

Other Linux

### OS Architecture

amd64 (on most hardwares)

### Session Type

Secure Session (Wayland, This is the default)

### Software Version

Latest release (I have run all updates)

### Log Output

```shell

```

### Hardware Info

_No response_