[tune/train] Implement new persistence strategy and roll out as default option

[ericl]

Implement the following REP: https://github.com/ray-project/enhancements/blob/main/reps/2023-06-06-simplify-sync.md

Subtasks:

• [tune/train] Remove URI parsing of paths #38568
• [tune/train] Add hard dependency on fsspec #38573
• [tune/train] Get rid of downsyncing path and download just the result.json / result.csv on result #38576
• [train] XGBoost, LightGBM, Sklearn Trainers to use train.report #38572
• [tune] Update PBT and BOHB to support _TrainingResult #38569
• [tune/train] Investigate default s3 filesystem performance with large files #38612
• [train][GA] Update ExperimentAnalysis for new persistence mode #38567
• [train][GA] Update CI tests to use new Checkpoint #38570
• [train][GA] Alias new Checkpoint to train.Checkpoint #38571
• [train][GA] Update release tests to use new Checkpoint #38574
• [train][GA] Remove rllib's ray.air.Checkpoint dependency #38575
• [train][GA] Update SyncConfig #38577
• [train][GA] Support Result.from_path w/o .tune_metadata file #38579
• [train][GA] Update Trainable.save_to_object to not depend on air.Checkpoint #38589

Related prs:

• [air] pyarrow.fs persistence: Introduce StorageContext and use it for driver syncing (1/n) #37690
• [air] pyarrow.fs persistence: Pass StorageContext to Train workers (2/n) #37909
• [air] pyarrow.fs persistence (3/n): Introduce new Checkpoint API #37925
• [air] pyarrow.fs persistence (4/n): Introduce a simplified checkpoint manager #37962
• [air] pyarrow.fs persistence (5/n): ray.train.Checkpoint save direction #37888
• [air] pyarrow.fs persistence (6/n): Fix Trial + Experiment paths to use the StorageContext #38057
• [air] pyarrow.fs persistence (7/n): ray.train.Checkpoint restore: Auto-recovery fault tolerance #38141
• [air] pyarrow.fs persistence (8/n): ray.train.Checkpoint restore: resume_from_checkpoint #38143
• [air] pyarrow.fs persistence (9/n): ray.train.Checkpoint restore: Manual restore #38128
• [air] pyarrow.fs persistence (10/n): Unify Tune and Train sessions to support new persistence path in FunctionTrainable #38284
• [air] pyarrow.fs persistence (11/n): Support pausing trials (and certain schedulers) #38355
• [air] pyarrow.fs persistence (12/n): Patch new persistence path for Class Trainable #38382
• [air] pyarrow.fs persistence (13/n): Support the Result.from_path API #38617
• [air] pyarrow.fs persistence (14/n): Simplified ExperimentAnalysis implementation #38648
• [tune/train] Get rid of downsyncing path and download just the result.json / result.csv on result #38598

[anyscalesam]

Keep this open until docs merge as part of RC tomorrow @justinvyu

[anyscalesam]

Docs are all merged!