Update chacha20: use ChaChaCore directly; remove bytes_until_reseed field #1614

Job	Run time
rustfmt	8s
test (windows-latest, x86_64-pc-windows-gnu, stable)	1m 30s
Clippy	24s
test (ubuntu-latest, x86_64-unknown-linux-gnu, stable)	30s
test-cross (ubuntu-latest, powerpc-unknown-linux-gnu, stable)	45s
Check doc	22s
test-miri	3m 34s
test-no-std	16s
test-ios	30s
test (ubuntu-latest, x86_64-unknown-linux-gnu, MSRV, 1.85.0)	35s
test (windows-latest, x86_64-pc-windows-msvc, beta)	1m 6s
test (macos-latest, x86_64-apple-darwin, stable)	42s
test (ubuntu-latest, sudo apt-get update ; sudo apt install gcc-multilib, i686-unknown-linux-gnu,...	53s
test (ubuntu-latest, x86_64-unknown-linux-gnu, nightly, minimal_versions)	42s
	11m 57s

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