d3d12decoder: Fix crash and resource barrier usage
d3d12decoder: Fix crash on flush
On flush event, baseclass will discard all pictures from DPB
but there can be still in-flight commands not finished yet.
Use our command queue, allocator and fence data helper objects
to keep resource available during command execution.
d3d12: Add {set,get}_user_data() methods to command allocator
d3d12decoder: Fix barrier usage
Common state promotion and decay does not seem to be applied to
decoder commands. Use barriers explicitly