Remove rand_core and use as external dependency; bump versions to 0.10.0-rc.1 #1474

Job	Run time
Check Clippy and rustfmt	24s
Check doc	22s
test-miri	3m 50s
test-ios	21s
test-cross (ubuntu-latest, powerpc-unknown-linux-gnu, stable)	1m 1s
test-no-std	14s
test (ubuntu-latest, x86_64-unknown-linux-gnu, stable)	35s
test (ubuntu-latest, sudo apt-get update ; sudo apt install gcc-multilib, i686-unknown-linux-gnu,...	1m 8s
test (windows-latest, x86_64-pc-windows-gnu, stable)	1m 34s
test (ubuntu-latest, x86_64-unknown-linux-gnu, nightly, minimal_versions)	43s
test (windows-latest, x86_64-pc-windows-msvc, beta)	1m 9s
test (ubuntu-latest, x86_64-unknown-linux-gnu, MSRV, 1.85.0)	33s
test (macos-latest, x86_64-apple-darwin, stable)	41s
	12m 35s

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