cache game rom/iso to ram new feature request

[degasus]

To be honest, there should be no need to cache all of the disk. The original disk is very slow, much slower than our hard disks right now (both in terms of latency and throughput). So we "just" need to implement the asynchron behavior in a good way. This is in contrast with the custom texture path. There the GPU reads from shared memory which is *much* faster than accessing the disk. Waiting for the harddrive is by far to slow there.