radv: use a winsys context per-queue, instead of per device v2

radv: use a winsys context per-queue, instead of per device v2

Queues are independent execution streams. The vulkan spec provides no
ordering guarantees for different queues.

By using a single context for all queues, we are forcing all commands
into an unecessary FIFO ordering.

This change is a preparation step to allow our-of-ordering scheduling of
certain work tasks.

v2: Fix a rebase error with radv_QueueSubmit() and trace_bo
Signed-off-by: Andres Rodriguez <andresx7@gmail.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>