DRI interface garbage collection, u_format extensibility

Do garbage collection on the exported DRI interface (it's mostly garbage) which is mostly taken from @anholt's !25665 (closed). I've taken her commits and nuked the backwards-compatibility notes, since @robclark has noted that we're actually OK to break the interface as minigbm's amdgpu can happily update when it uprevs Mesa, especially as most of the changes are pretty cosmetic.

It also doesn't include any of the earlier changes related to DRI_IMAGE_FORMAT, since I've been going a different way. This series culminates in converting u_format.csv to u_format.yaml so it can be extended without breaking anyone's brain. I've verified that the generated code is identical from both as well as preserved the comments, so of course it is thus perfect and has no bugs.