Add `OsRng::{seed, try_seed}` #1476

Job	Run time
test-cross (ubuntu-latest, powerpc-unknown-linux-gnu, stable)	57s
Check doc	20s
Check Clippy and rustfmt	15s
test (ubuntu-latest, x86_64-unknown-linux-gnu, stable)	32s
test (windows-latest, x86_64-pc-windows-gnu, stable)	1m 14s
test (ubuntu-latest, sudo apt-get update ; sudo apt install gcc-multilib, i686-unknown-linux-gnu,...	1m 1s
test (windows-latest, x86_64-pc-windows-msvc, beta)	1m 39s
test (ubuntu-latest, x86_64-unknown-linux-gnu, MSRV, 1.85.0)	35s
test (ubuntu-latest, x86_64-unknown-linux-gnu, nightly, minimal_versions)	41s
test (macos-latest, x86_64-apple-darwin, stable)	1m 13s
test-ios	19s
test-no-std	19s
test-miri	4m 1s
	13m 6s

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