v3dv: add a blit fallback path for vkCmdResolveImage

This fallback is required when we have to do partial resolves. It
works the same way as other blit fallbacks for copy operations: it
will bind the source image as a source texture and blit the selected
region to the destination image.

The difference in this case is that the source image is multisampled
and the blit shader needs to fetch and average individual samples for
each texel.

This gets us to pass all the remaining test cases in
dEQP-VK.api.copy_and_blit.core.resolve_image.*

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6766>
2 files changed