Submit current command buffer in wined3d_context_vk_get_command_buffer()
and return a new one if the total size of retired buffer objects on that
command buffer crosses a predefined threshold.

One way this issue may arise is when an application, by repeatedly doing
resource updates, does not trigger a flush of the command buffer and
accumulates transient staging buffers.
Signed-off-by: Jan Sikorski <jsikorski@codeweavers.com>
Signed-off-by: Henri Verbeet <hverbeet@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>