Asset Lifetime v3 - Asynchronous/streaming loads

[leggettc18]

Kenix3

• Asynchronously load the room for the nearest exit whenever you are in a scene, and unload the previous nearest room when applicable. When going to a new room the previous room should always be the closest room until Link moves. If Link reaches the exit while the asynch load is going on, freeze him and load the next room synchronously
• GI link over head do an asynchronous load while the animation is playing, then promote that to synchronous when the item will display. Unload when the item is no longer rendered and Link is not holding the item up anymore, assuming there is not also a freestanding item that needs that object. We will also need to change it so we don't load all HD GI objects at game boot.

[Malkierian]

First point is partially addressed with #4652. Because asset load is initiated at the start of scene transition, it's enough time for most machines to get all the assets loaded in before they're needed in the next scene, even with the 4K Reloaded pack. If that isn't enough, we can re-address proximity loading, but it may not be necessary anymore.
As to the second point, is immediate unload actually a priority anymore? I see no reason not to just keep GIs persisted, at least from a memory standpoint.