* Remove flooring in v3 scheduler code
It is no longer supposed to be an exact port of the old Python code.
* Rework v3 fuzzing
https://github.com/ankitects/anki/issues/1416#issuecomment-958208149
* Ensure length of fuzz range is larger than 1
Only for new intervals larger than 1 and respecting max review interval.
* add the beginnings of a unit test
* Clarify `fuzz_factor` doc string
* Fix Python tests for 2021 scheduler
* Fix fuzz test
1.0 is not a valid fuzz factor.
* Add tests for fuzzing in Rust
* Use range notation in fuzz factor doc
* Strip redundant tests
- Currently we just use 1.5x and 2x the normal preview delay; we could
change this in the future.
- Don't try to capture the current state; just use a flag to denote
exit status.
- Show (end) when exiting