Tests

Support using std without getrandom or rand_chacha #614

Job	Run time
Check doc	1m 50s
test (ubuntu-latest, x86_64-unknown-linux-gnu, stable)	1m 45s
test-ios	46s
test (macos-latest, x86_64-apple-darwin, stable)	2m 24s
test-cross (ubuntu-latest, powerpc-unknown-linux-gnu, stable)	1m 53s
test-miri	4m 58s
test-no-std	18s
test (windows-latest, x86_64-pc-windows-gnu, stable)	4m 16s
test (windows-latest, x86_64-pc-windows-msvc, beta)	3m 1s
test (ubuntu-latest, x86_64-unknown-linux-gnu, MSRV, 1.60.0)	4m 14s
test (ubuntu-latest, sudo apt-get update ; sudo apt install gcc-multilib, i686-unknown-linux-gnu,...	2m 1s
test (ubuntu-latest, x86_64-unknown-linux-gnu, nightly, minimal_versions)	2m 35s
	30m 1s

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