Deprecate and rename schema/x/types packages

[dmathieu]

Description

The revive linter is unhappy with the types packages in schema, as it's understandably too generic.
#6841

We're about to ignore the issue: #6868

However, the entire schema package is experimental, so we should be able to deprecate and rename the package (technically, we shouldn't even need to deprecate, but that's a rather trivial thing to do here).

I'm looking for package name ideas. I'm thinking about model, but that doesn't seem so great.

[pellared]

Related to:

• schema: redesign v* package layout #4534