Fixes to SOGS data unloading

[mvaligursky]

• handle case when SOGS resource is waiting for async GPU processing and gets destroyed - skip early from unfinished processing, don't create resource when device / textures were destroyed
• while still GPU processing, postpone deletion of objects to avoid crashes, and destroy at the end
• when SOGS resource unloads, unload texture resources it created
• similarly, when the device is destroyed, cleanly handle async texture download

[saurabh-vh]

Please can anyone explain me what is SOGS. I am newbee