Reequip gear item after teleporting

[Meivyn]

This is the only thing I am missing from your addon, which is arguably the most complete teleport addon out there. So here it is.
Note that ITEM_LOCK_CHANGED had to be registered early, as this event sometimes might be fired before OnClick and PostClick for some reason. So I couldn't rely on click handlers to achieve that.

Also ClearAllInvalidHighlights should probably be renamed to RefreshHighlights as it should take care of highlighting as well. You previously highlighted twice in the handler.

Using ZONE_CHANGED_NEW_AREA also has the advantage of ensuring the player reequips their item if they change their mind and doesn't teleport after clicking once.

[Justw8]

I am currently on holiday until the end of November, can you bump this PR if I forget about it come december?

[Meivyn]

Anyway, I'll be reworking it a bit. Avoid merging for now. Might be unrelated to this PR, but there are issues with highlight/cooldown check that need to be addressed.

[Meivyn]

So to explain the recent changes:

• UNIT_SPELLCAST_SUCCEEDED is used to avoid the case where the player might not get into a new zone. For instance, when the player wants to teleport back to the main area of the Timeless Isle rapidly after killing Ordos.
• SPELL_UPDATE_COOLDOWN is used to update the cooldown of all buttons in real-time. Previously, it was required to toggle the menu again, and it was pretty unreliable on refreshing the cooldowns. Cooldown info isn't available in UNIT_SPELLCAST_SUCCEEDED so it can't be used for that.
• ZONE_CHANGED_NEW_AREA is used as a fallback to ensure that the player unequips any teleportation item, no matter what. It also avoids unnecessarily listening for casts forever. If the player changes their mind and wants to teleport somewhere else for example, or if they choose to stay where they are and don't complete the teleport cast at all.
• PLAYER_EQUIPMENT_CHANGED is used to refresh the highlight. This is needed for it to work properly in real-time. It is also used to know when original item info data can be queried. It also refreshes cooldowns, as some items get a cooldown when they are equipped.
• PLAYER_REGEN_ENABLED is used to try to reequip the item in case they are in combat when EquipItemByName is called, which would cause it to pickup the item rather than equipping it.
• ITEM_LOCKED is used because by the time PostClick is fired, the info we need is already gone. Do note that this code does rely on the visibility check; if the frame becomes visible by any other means than hovering the flyout, it might introduce subtle bugs.

I tried to avoid doing work such as refreshing cooldowns and refreshing highlights when the buttons are not visible, but this seems to be required for it to work. I can't think of any other side case where this stuff wouldn't work; it's a bit more verbose, but it's to ensure reliability.