* Improve typing for Generators and Async Generators
* Add TReturn and TNext to Iterator, IterableIterator, etc.
* Update ts internal Iterator to be assignable from global Iterator
* Make 'done' optional in IteratorYieldResult
* Revert Iterable and IterableIterator to simpler versions plus other fixes
* Add additional inference tests
* Added additional tests
* PR cleanup and minor async iteration type fix
* Updated diagnostics message and added non-strict tests
* Fix expected arity of Iterator/AsyncIterator
