feat(all): enable REGAPIC and REST numeric enums

[noahdietz]

Enables REGAPIC and REST numeric enum serialization for all API clients, except for those that are known to only support one transport / not support REST numeric enum serialization.

["grpc", "rest"] is now the default set of transports generated for a package. REST numeric enum serialization is enabled by default. As such, this removes all explicit Transports instances that match the new default.

Note: There are three beta-level packages that will take breaking changes in a follow-up PR that remove REST support.

[quartzmo]

Thank you for simplifying the config! 🎉

[noahdietz]

I regenerated everything, pushed it to this PR, and kokoro was appeased. There was an issue with vet.sh which was my lack of gofmt prior to pushing. I've since reverted the generated changes to allow our job to do it.

[noahdietz]

Similarly, I saw in a #7148 apidiff run on all affected packages we should not have any breaking changes in the next regen using this new config. There will be some follow up PRs to break a few clients that must be broken per the findings of #7148 .