Add Delete Profile button with confirmation, hide CoAMultiCastActionBarFrame

- Add CoAMultiCastActionBarFrame to HideCoA.FRAMES so it gets a checkbox
  in both the Classes and Character Override tabs automatically.
- Add a Delete Profile button next to the override profile dropdown,
  disabled for the currently logged character's own profile (with an
  explanatory text shown below the row in that case).
- Confirm deletion via a StaticPopupDialog before removing a profile.
- Revert the Classes tab box backdrop under ElvUI back to the original
  borderless style; keep the new bordered style for the non-ElvUI case.

HideCoA.lua

@@ -30,6 +30,7 @@ HideCoA.FRAMES = {
     "CoAResourceSegmentBar",
     "CoAResourceOrb",
     "CoAResourceBar",
+    "CoAMultiCastActionBarFrame",
 }
 
 local function CreateDefaultClassSettings()