Tests

Remove SmallRng::from_thread_rng (#1532) #1175

Job	Run time
test-cross (ubuntu-latest, powerpc-unknown-linux-gnu, stable)	1m 16s
Check doc	33s
test (ubuntu-latest, x86_64-unknown-linux-gnu, stable)	1m 0s
test-ks	37s
test (macos-latest, x86_64-apple-darwin, stable)	1m 8s
test-miri	4m 30s
test (windows-latest, x86_64-pc-windows-gnu, stable)	3m 24s
test (windows-latest, x86_64-pc-windows-msvc, beta)	2m 10s
test (ubuntu-latest, x86_64-unknown-linux-gnu, MSRV, 1.61.0)	2m 53s
test (ubuntu-latest, sudo apt-get update ; sudo apt install gcc-multilib, i686-unknown-linux-gnu,...	1m 44s
test (ubuntu-latest, x86_64-unknown-linux-gnu, nightly, minimal_versions)	1m 25s
test-ios	23s
test-no-std	15s
	21m 18s

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