Move `AvroType` to separate sub-projects

[nevillelyh]

trafficstars

To make ways for Scala 3 migration.

[nullobject]

For the time being, will 0.10.x packages for the bigquery subproject be published to maven?

[regadas]

With 0.10.x they are published as scio-google-cloud-platform.

If you are moving to this release, have a look at https://spotify.github.io/scio/migrations/v0.10.0-Migration-Guide.html since there are a few other changes.

[nullobject]

@regadas Thanks, exactly what I was looking for :+1:

[jto]

I'm working on the AvroType part.

[RustedBones]

Probably a won't do if we move away from macros in favor of magnolify