Asset creation threading issue.

[maluoi]

Description

Asset allocation is currently not thread safe. In practice, I've not seen or heard this being a problem, but in stress tests, it can be consistently reproduced. It's probably one of those annoying things that happens once every 1000 runs.

I believe the core issue is that assets are all added and removed from a single core list when they're created, and this list is not thread safe. Most assets do have thread safety built into their own implementations, but this shared list never accounted for it.