2 minute hang and high memory usage when adding assets with large textures

2 minute (or more) hang and high memory usage when adding assets with large textures. The memory increase can be up to 3 or 4 GB when none of these assets(or referenced assets) take up nearly that much memory. It goes back down after the hang is over, but on some computers, that kind of memory increase can cause problems.

[NameRemoved]:- This is a result of compressing very large 8kx8k textures on first import. Using CUDA version of the compressor is not an option, due to the possibility of breaking deterministic cooking. So make the texture compression async to hide the stall.

1. Create a blank project in 4.8 preview 4
2. Download the Open World Demo Colleciton
3. Add the content to the blank project
4. Open the project
5. In the content browser, navigate to Environments>Rocks
6. Select any of the first few folders
7. Bring up task manager
8. Attempt to drag one of the static meshes into the level

Result: Memory usage rockets up from around 500MB to about 3.5GB and the editor hangs for up to 2 minutes (I timed it)

Unreal Engine 4.7.5 Lag on adding things to scene