Fixes a merge conflict that broke stat panel (#96071)

## About The Pull Request

Fixes a merge conflict between 2 of my stat panel PRs that caused the
'Toggle Stat Panel' button to not work.
Also converts more skin stuff to defines that I missed in the last PR.

## Why It's Good For The Game

Button works wahoo!

## Changelog

🆑
fix: Stat panel's "Toggle Stat Panel" button now works.
/🆑

code/modules/tooltip/tooltip.dm

@@ -19,7 +19,7 @@ Notes:
 
 /datum/tooltip
 	var/client/owner
-	var/control = "mainwindow.tooltip"
+	var/control = SKIN_MAINWINDOW_TOOLTIP
 	var/showing = 0
 	var/queueHide = 0
 	var/init = 0