This removes calls to `arc4random` and `arc4random_uniform` and replaces
them with calls to `Int.random` or equivalent.
These are a little less readable, which may be [why SwiftLint doesn't
like them][0]. (SwiftLint calls them "legacy", possibly because they're
not strong random number generators, but I couldn't find a clear
explanation for this anywhere, including [the original PR][1].)
This is the kind of change that's error-prone, so I wrote [a simple
script to help avoid regressions][2]. The script runs 10,000 iterations
of the old and new RNG and compares the ranges, reporting differences.
(Some differences are likely, like the ones that involve floats; others
are very unlikely to have differences.)
`git grep arc4random | grep swift` returns no results after this change.
Same for [everything else SwiftLint checks for][3].
[0]: https://realm.github.io/SwiftLint/legacy_random.html
[1]: https://github.com/realm/SwiftLint/pull/2419
[2]: https://gist.github.com/EvanHahn-Signal/9c75c9f484f4778149cbde3eafc9b285
[3]: ea6cc50890/Source/SwiftLintFramework/Rules/Idiomatic/LegacyRandomRule.swift (L23-L27)
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