bar_cmd_tray_bind: Use mouse button helpers

This modifies `bar_cmd_tray_bindsym` to use `get_mouse_bindsym` for
parsing mouse buttons. This also introduces `bar_cmd_tray_bindcode`,
which will use `get_mouse_bindcode` for parsing mouse buttons. Like with
sway bindings, the two commands are encapsulated in a single file to
maximize shared code.

This also modifies tray bindings to work off of events codes rather than
x11 buttons, which allows for any mouse buttons to be used.

For `get_bar_config`, `event_code` has been added to the `tray_bindings`
section and will include to event code for the button. If the event code
can be mapped to a x11 button, `input_code` will still be the x11 button
number. Otherwise, `input_code` will be `0`.

swaybar/input.c

@@ -22,6 +22,31 @@ void free_hotspots(struct wl_list *list) {
 	}
 }
 
+uint32_t event_to_x11_button(uint32_t event) {
+	switch (event) {
+	case BTN_LEFT:
+		return 1;
+	case BTN_MIDDLE:
+		return 2;
+	case BTN_RIGHT:
+		return 3;
+	case SWAY_SCROLL_UP:
+		return 4;
+	case SWAY_SCROLL_DOWN:
+		return 5;
+	case SWAY_SCROLL_LEFT:
+		return 6;
+	case SWAY_SCROLL_RIGHT:
+		return 7;
+	case BTN_SIDE:
+		return 8;
+	case BTN_EXTRA:
+		return 9;
+	default:
+		return 0;
+	}
+}
+
 static uint32_t wl_axis_to_button(uint32_t axis, wl_fixed_t value) {
 	bool negative = wl_fixed_to_double(value) < 0;
 	switch (axis) {