Uses the new AIR Train API for examples and tests.
The `Result` object gets a new attribute - `log_dir`, pointing to the Trial's `logdir` allowing users to access tensorboard logs and artifacts of other loggers.
This PR only deals with "low hanging fruit" - tests that need substantial rewriting or Train user guide are not touched. Those will be updated in followup PRs.
Tests and examples that concern deprecated features or which are duplicated in AIR have been removed or disabled.
Requires https://github.com/ray-project/ray/pull/25943 to be merged in first
