Support Rekorv2 types

[ramonpetgrave64]

Client support for Rekor V2: sigstore-python #289

RekorV2's openapi specs are now hosted in the sigstore/rekor-tiles repo.

• https://github.com/sigstore/rekor-tiles/blob/6ab405027c9f7969c96fe0f82e111058a978bd2e/docs/openapi/rekor_service.swagger.json

We must support the new types that define the request and response structures.

[jku]

This codegen business is not my strength so this may be a dumb question but do we necessarily want to use the openapi specs (since this seems to have its own technical issues)?

rekor-tiles API is defined in protobufs so using those seems fairly natural: https://github.com/sigstore/rekor-tiles/tree/main/api/proto

[ramonpetgrave64]

To update, rekor-tiles can now generate python types. the goal is to get them checked into sigstore/protobuf-specs, but so far an example can be seen here sigstore/sigstore-python#1400