river: add rules system

This is a breaking change and replaces the previous
csd-filter-add/remove and float-filter-add/remove commands.

See the riverctl(1) man page for documentation on the new system.

river/Cursor.zig

@@ -877,7 +877,7 @@ fn processMotion(self: *Self, device: *wlr.InputDevice, time: u32, delta_x: f64,
 
             {
                 // Modify the pending box, taking constraints into account
-                const border_width = if (data.view.pending.borders) server.config.border_width else 0;
+                const border_width = if (data.view.pending.ssd) server.config.border_width else 0;
 
                 var output_width: i32 = undefined;
                 var output_height: i32 = undefined;