Generate protobuf types with Hybrid API

[johanbrandhorst]

With Go protobuf v1.36.0 the new Opaque API was introduced. We can't move to the Opaque API as our users may import the generated files and it would be a breaking change. We can, however, generate our protobuf files with the Hybrid API.

See https://opaque-preview.stapelberg.ch/go.dev/blog/protobuf-opaque for more information.