Instead of creating the op manually, just pass in the renderpass and
have the op created from there.
This way ops aren't really initialized anymore, they are more appended
to the queue, so instead of foo_op_init() we can just call the function
foo_op().
GskVulkanOp is meant to be a proper abstraction of operations
the Vulkan renderer will be doing.
For now it's an atrocious clunky piece of junk wedged into the
renderpass codebase.
It's so temporary that I didn't even adjust indentation of the code.
