(fix/WeakAuras): Resolve long-standing frame level overflow

Switches frame level assignment to depth-based ordering to avoid overflow
and ensure deterministic ordering. WeakAurasFrame now correctly lives on
FrameStrata MEDIUM without interfering with Blizzard UI elements.

(cherry picked from commit e92edf5700ad70587a71c3a403e5cc672dbc9e8e)

WeakAuras/RegionTypes/Group.lua

@@ -21,6 +21,7 @@ local default = {
   borderSize = 2,
   borderBackdrop = "Blizzard Tooltip",
   scale = 1,
+  sharedFrameLevel = true, -- true to ensure identical behavior on newer clients
 };
 
 Private.regionPrototype.AddAlphaToDefault(default);