Rework Private Aura handling

[nebularg]

Setting the private auras in the module is now an API call in the main chunk that passes a table of settings. Positional arg for aura id, and some named args: option to set the tooltip spell id (if the private aura has no description), mythic to show the mythic icon next to the name in the spell list, extra to provide a table of spell ids if there are multiple used.

mod:SetPrivateAuraSounds({
    420544, -- Scorching Pursuit
    {425888, mythic = true}, -- Igniting Growth
    {407182, option = 407221}, -- Rushing Darkness
    {414186, extra = {414187, 421825, 421826, 421827, 421828, 421829}}, -- Blaze
})

• Moves private aura sound settings to an encounter dropdown entry

• Removes the default ME_ONLY and ME_ONLY_EMPHASIZE ability options when the PRIVATE flag is set

• Also adds a new sound category for Private Auras (but not a new sound)