[9/n] CommandBufferStagingStream: for VulkanQueueSubmitWithCommands

Bug: 177241396

This new subclass of IOStream will not be used to send anything to the
host, but instead serves as an intermediate buffer to hold Vulkan
vkCmd*'s.

Change-Id: I2ecdc05f885862ab82150741214c385bfa01002e
4 files changed