Makes it easier to identify the command stream thread and the
queue processing thread easier when using a wine build that
supports SetThreadDescription.
* [util] Adds getTempDirectory() function
Will be used by on-disk pipeline caching
* [dxvk] Implement on-disk shader caching
Saving the pipeline cache to disk when the application exits
should be sufficient but the DxvkPipelineCache destructor isn't
reliably called on exit (ref-counting issue?).
As a workaround every frame we check and save the cache if the
size increased by some amount or after one minute elapsed.
* [dxvk] Periodically update shader cache file in separate thread
