A minor release that fixes some issues identified in RC18:
- `RuntimeunsafeRunToFuture` would auto-interrupt futures quickly due to supervision
- There was no way to construct `ZEnv` outside `ZLayer`; now the default runtimes come equipped with `ZEnv`
- The supervision model has been simplified (`SuperviseMode` is gone since it was redundant with other features)
- Root fibers are now tracked weakly so are less prone to leaking
- Some callback type signatures have been relaxed, to avoid forcing a return of `Unit` on the user
- `ZIO.adopt` was added as the inverse of `ZIO.disown`
- More scaladoc has been added
- Parallel ZLayer construction is disabled until an issue with auto-killing is fixed
- More combinators added to `ZLayer`, such as `fail`, `orElse`, `orDie`; and the `Has` constraint dropped on the output, required only for composition of layers
- Mocking component in ZIO Test got a totally new overhaul that removes the need for implicits and allows many more powerful ways of creating expectations (all of, any of, etc.)