Tests

Add .choices() method to the Slice distribution #700

Job	Run time
test-miri	2m 16s
test (ubuntu-latest, x86_64-unknown-linux-gnu, stable)	59s
test (macos-latest, x86_64-apple-darwin, stable)	1m 23s
Check doc	1m 4s
test-cross (ubuntu-latest, powerpc-unknown-linux-gnu, stable)	1m 18s
test-ios	27s
test (windows-latest, x86_64-pc-windows-gnu, stable)	2m 17s
test (windows-latest, x86_64-pc-windows-msvc, beta)	1m 44s
test-no-std	13s
test (ubuntu-latest, x86_64-unknown-linux-gnu, MSRV, 1.60.0)	4m 25s
test (ubuntu-latest, sudo apt-get update ; sudo apt install gcc-multilib, i686-unknown-linux-gnu,...	1m 37s
test (ubuntu-latest, x86_64-unknown-linux-gnu, nightly, minimal_versions)	36s
	18m 19s

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