Apply rustfmt and fix Clippy warnings #832

Job	Run time
test-miri	3m 26s
test-cross (ubuntu-latest, powerpc-unknown-linux-gnu, stable)	1m 16s
Check doc	1m 8s
test (ubuntu-latest, x86_64-unknown-linux-gnu, stable)	54s
test-ios	20s
test (macos-latest, x86_64-apple-darwin, stable)	44s
test (windows-latest, x86_64-pc-windows-gnu, stable)	1m 45s
test (windows-latest, x86_64-pc-windows-msvc, beta)	1m 30s
test-no-std	11s
test (ubuntu-latest, x86_64-unknown-linux-gnu, MSRV, 1.61.0)	2m 50s
test (ubuntu-latest, sudo apt-get update ; sudo apt install gcc-multilib, i686-unknown-linux-gnu,...	1m 47s
test (ubuntu-latest, x86_64-unknown-linux-gnu, nightly, minimal_versions)	1m 32s
	17m 23s

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