update rand and quickcheck
update rand and quickcheck

Summary:
This updates the following crates to their latest versions:
- `rand`: 0.7 => 0.8
- `quickcheck`: 0.9 => 1.0

Both crates introduced some breaking changes, so affected clients had to be fixed accordingly. Most changes are rather mechanical and shouldn't change the existing logic. In addition, a few buggy property tests were uncovered, presumably due to `quicktest` becoming smarter with its choice of inputs in the newer version, and the fixes are included in this diff.

Reviewed By: yancouto

Differential Revision: D31115820

fbshipit-source-id: 60a61dfac3236fd93cd4f03b86506654d81d330f

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