Fix Clippy warnings and enable Clippy in CI. (#1216) #2732

Job	Run time
softhsm2-test (1.70.0, hsm,hsm-tests-pkcs11)	5m 43s
build (ubuntu-latest, 1.70.0, --no-default-features)	7m 4s
softhsm2-test (stable, hsm,hsm-tests-pkcs11)	4m 53s
pykmip-test (1.70.0, hsm)	5m 41s
build (ubuntu-latest, 1.70.0)	8m 45s
softhsm2-test (beta, hsm,hsm-tests-pkcs11)	5m 11s
pykmip-test (1.70.0, hsm,hsm-tests-kmip)	6m 13s
build (ubuntu-latest, 1.70.0, --features all)	8m 25s
pykmip-test (stable, hsm)	5m 24s
build (ubuntu-latest, stable, --no-default-features)	6m 37s
pykmip-test (stable, hsm,hsm-tests-kmip)	5m 22s
build (ubuntu-latest, stable)	8m 8s
build (ubuntu-latest, stable, --features all)	8m 52s
pykmip-test (beta, hsm)	5m 17s
build (ubuntu-latest, beta, --no-default-features)	6m 26s
pykmip-test (beta, hsm,hsm-tests-kmip)	5m 33s
build (ubuntu-latest, beta)	8m 12s
build (ubuntu-latest, beta, --features all)	7m 39s
	1h 59m 25s

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