wayland/layershell: refactor layer shell surface integration

In addition to the much needed cleanup:

- The bridge/extension type is now directly tied to the QWindow
instead of the WlrLayershell object, and is much smaller.
- Layer requests are now comitted via polish instead of for each
change individually.

src/wayland/module.md

@@ -1,8 +1,7 @@
 name = "Quickshell.Wayland"
 description = "Wayland specific Quickshell types"
 headers = [
-	"wlr_layershell/window.hpp",
-	"wlr_layershell.hpp",
+	"wlr_layershell/wlr_layershell.hpp",
 	"session_lock.hpp",
 	"toplevel_management/qml.hpp",
 	"screencopy/view.hpp",