Apply rustfmt and fix Clippy warnings #820

Job	Run time
test-miri	3m 58s
test-no-std	14s
test-cross (ubuntu-latest, powerpc-unknown-linux-gnu, stable)	1m 22s
test (ubuntu-latest, x86_64-unknown-linux-gnu, stable)	38s
Check doc	1m 7s
test (macos-latest, x86_64-apple-darwin, stable)	39s
test-ios	20s
test (windows-latest, x86_64-pc-windows-gnu, stable)	1m 38s
test (windows-latest, x86_64-pc-windows-msvc, beta)	1m 13s
test (ubuntu-latest, x86_64-unknown-linux-gnu, MSRV, 1.61.0)	2m 28s
test (ubuntu-latest, sudo apt-get update ; sudo apt install gcc-multilib, i686-unknown-linux-gnu,...	1m 27s
test (ubuntu-latest, x86_64-unknown-linux-gnu, nightly, minimal_versions)	1m 13s
	16m 17s

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