[air/tune] Add top-level imports for Tuner, TuneConfig, move CheckpointConfig

[krfricke]

Signed-off-by: Kai Fricke [email protected]

Why are these changes needed?

This exposes Tuner and TuneConfig to the top-level ray.tune scope and moves checkpoint config to ray.air.config. This PR fixes circular imports.

Related issue number

Closes #24703

Checks

• I've run scripts/format.sh to lint the changes in this PR.
• I've included any doc changes needed for https://docs.ray.io/en/master/.
• I've made sure the tests are passing. Note that there might be a few flaky tests, see the recent failures at https://flakey-tests.ray.io/
• Testing Strategy
  • Unit tests
  • Release tests
  • This PR is not tested :(

[xwjiang2010]

Nice, thank you Kai!

[krfricke]

Linter is currently failing:

ray.util.client.common.ActorOptionWrapper
ray.util.client.common.ClientActorClass
ray.util.client.common.ClientActorHandle
ray.util.client.common.ClientActorRef
ray.util.client.common.ClientObjectRef
ray.util.client.common.ClientRemoteFunc
ray.util.client.common.ClientRemoteMethod
ray.util.client.common.ClientServerHandle
ray.util.client.common.ClientSideRefID
ray.util.client.common.ClientStub
ray.util.client.common.InProgressSentinel
ray.util.client.common.OptionWrapper
ray.util.client.common.OrderedResponseCache
ray.util.client.common.ResponseCache
ray.util.client.common.remote_decorator
ray.util.client.common.return_refs
ray.util.client.common.set_task_options
ray.util.client.options.validate_options
ray.util.placement_group.check_placement_group_index

@ericl can you advise?

[ericl]

Those are valid linter checks. I would make a PR to move util.client to an _internal package, or otherwise avoid depending on that package for now.

[xwjiang2010]

Should we also add "ResultGrid" to top level?

[richardliaw]

I'm going to try reverting the change to util to unblock this PR; we can remove clean it up from util separately.