tu: Rewrite flushing to use barriers

tu: Rewrite flushing to use barriers

Replace the various ad-hoc flushes that we've inserted, copied from
freedreno, etc. with a unified system that uses the user-supplied
information via vkCmdPipelineBarrier() and subpass dependencies.

There are a few notable differences in behavior:

- We now move setting RB_CCU_CNTL up a little in the gmem case, but
hopefully that won't matter too much. This matches what the Vulkan blob
does.

- We properly implement delayed setting of events, completing our
implementaton of events.

- Finally, of course, we should be a lot less flush-happy. We won't emit
useless CCU/cache flushes with multiple copies, renderpasses, etc. that
don't depend on each other, and also won't flush/invalidate the cache
around renderpasses unless we actually need to.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4964>