fix: enable stance/state bars for CoA custom classes with shapeshift forms

Vanilla Bartender4 assumes only DRUID/WARRIOR/WARLOCK/PRIEST/ROGUE/HERO have
shapeshift forms. CoA custom classes (Witchdoctor, Templar, …) can register
forms late at runtime and aren't in the whitelist, so the stance/state bar
never came up for them.

StanceBar.lua:
  - ApplyConfig() no longer Disable()s the module when GetNumShapeshiftForms()
    is 0 at config time. A disabled module never re-enables on
    UPDATE_SHAPESHIFT_FORMS, so late-registered forms were lost. We now just
    hide the bar frame.
  - Register UPDATE_SHAPESHIFT_FORMS and PLAYER_ENTERING_WORLD on the module
    itself and re-Enable() / show the bar when forms appear after the fact.

Options/Bar.lua:
  - The 'Hide in Stance/Form' visibility option was gated by a hard-coded
    stanceClasses whitelist. Add an OR-fallback on GetNumShapeshiftForms() > 0
    so CoA classes with forms get the UI.

StateBar.lua:
  - DefaultStanceMap only had vanilla entries. For unknown classes with live
    forms, synthesise a generic { id="formN", index=N } map at runtime so
    UpdateStates() can wire stance-based action bar swaps.

Bartender4/Options/Bar.lua

@@ -344,7 +344,10 @@ function Bar:GetOptionObject()
 					name = L["Hide in Stance/Form"],
 					desc = L["Hide this bar in a specific Stance or Form."],
 					values = getStanceTable,
-					hidden = function() return (not stanceClasses[class]) end,
+					-- CoA: custom classes (Witchdoctor, Templar, …) may have forms
+					-- but aren't in the vanilla stanceClasses whitelist. Show the
+					-- option whenever the player currently has any form available.
+					hidden = function() return (not (stanceClasses[class] or GetNumShapeshiftForms() > 0)) end,
 					disabled = customEnabled,
 				},
 				customNl = {