A managed byte slice from the new byte slice pool has a function
to release and put it back to the pool explicitly, and this doesn't
rely on GCs.
Updates #1681Closes#2804
Bytes from a pool in a command queue is now pretty hard to use correctly
as the lifetime of a queue is not clear.
Remove the byte pools once. Let's reconsider pool usages later.
This change also removes imagesWithBuffers as this is no longer needed.
imagesWithBuffers was necessary to ensure all the bytes from the pool
of the command queue was used before the queue flushes the commands,
as the command queue cleared the pool after flushing. The lifetimes
were pretty ticky.