wayland: implement scaling

This involves many subsystems:

- config:
    - allow setting the connector scale
    - allow setting the cursor size
- cursors:
    - load server cursors for all requested sizes and scales
- wl_surface:
    - track the output the surface belongs to
    - send wl_surface.enter/leave
- wl_output:
    - implement wl_output.scale
- text:
    - pre-render texts for all used scales
- renderer:
    - properly align scale textures and rectangles
- wp_fractional_scale:
    - new interface for fractional scaling

jay-config/src/_private/ipc.rs

@@ -274,6 +274,20 @@ pub enum ClientMessage<'a> {
         device: InputDevice,
         px: f64,
     },
+    ConnectorSetScale {
+        connector: Connector,
+        scale: f64,
+    },
+    ConnectorGetScale {
+        connector: Connector,
+    },
+    ConnectorSize {
+        connector: Connector,
+    },
+    SetCursorSize {
+        seat: Seat,
+        size: i32,
+    },
 }
 
 #[derive(Encode, Decode, Debug)]
@@ -360,6 +374,13 @@ pub enum Response {
     GetFont {
         font: String,
     },
+    ConnectorGetScale {
+        scale: f64,
+    },
+    ConnectorSize {
+        width: i32,
+        height: i32,
+    },
 }
 
 #[derive(Encode, Decode, Debug)]