Various cleanup

Removes version compatibility checks for TBC/Vanilla, consolidating code to target a single WoW version. Refactors repetitive SetWidth/SetHeight calls to SetSize for cleaner code. Removes duplicate function definitions from unitxp module and simplifies conditional show/hide operations using SetShown.

api/api.lua

@@ -64,6 +64,10 @@ end
 -- Requires UnitXP_SP3
 function pfUI.api.UnitInLineOfSight(unit1, unit2)
   if not pfUI.api.HasUnitXP() then return nil end
+  if not unit2 then
+    unit2 = unit1
+    unit1 = "player"
+  end
   local success, inSight = pcall(UnitXP, "inSight", unit1, unit2)
   if success then return inSight end
   return nil
@@ -74,6 +78,10 @@ end
 -- Requires UnitXP_SP3
 function pfUI.api.UnitIsBehind(unit1, unit2)
   if not pfUI.api.HasUnitXP() then return nil end
+  if not unit2 then
+    unit2 = unit1
+    unit1 = "player"
+  end
   local success, behind = pcall(UnitXP, "behind", unit1, unit2)
   if success then return behind end
   return nil