Handle new code gen for rekor v2 protos

[loosebazooka]

Follow up to #661

Would be helpful for language client owners to check if their builds are still "complete". Especially ruby and typescript, I'm not sure exactly what needs to be done there.

• java (@loosebazooka)
• ruby (@segiddins) (context)
• typescript (@bdehamer) (context)
• rust (@jku)
• python (@jku)
• go

[jku]

Python lgtm and the rekor v2 types seem to work fine. I'm not going to promise that for rust (looks fine but Im no expert and have not tested)