Reduce number of distributed tests.

[justinxzhao]

Ludwig distributed unit tests frequently exceed the 50 minute timeout.

Some tests seem like they don't need to be distributed, while in other cases overparameterization can be wasteful.

Primary changes:

• Refactored ray-related automl utilities into a separate library, i.e. ray_utils.py, enabling type inference tests to run non-distributed.
• Reduced the number of hyperopt tests by decreasing the parameterization spaces for search algorithms and schedulers.
• Un-distribute tests where they don't need to be distributed.

[github-actions]

Unit Test Results

       6 files  +    2         6 suites  +2   2h 21m 35s ⏱️ + 49m 35s
2 912 tests  -   18  2 866 ✔️  -   18    46 💤 ±  0  0 ❌ ±0 
8 736 runs  +288  8 594 ✔️ +242  142 💤 +46  0 ❌ ±0 

Results for commit 7108501. ± Comparison against base commit 6ee335f.

♻️ This comment has been updated with latest results.