Rust

Add `ContigousBitset64` container type. #703

Job	Run time
Test on i686-unknown-linux-gnu with cross	1m 10s
Test with miri	1m 5s
Test with -Zsanitizer=address	43s
Test with -Zsanitizer=memory	43s
Test Rust 1.34.0 on ubuntu-latest	5m 48s
Test Rust 1.61.0 on ubuntu-latest	6m 29s
Test Rust beta on ubuntu-latest	14s
Test Rust stable on ubuntu-latest	14s
Test Rust stable on windows-latest	34s
Test Rust stable on macos-latest	13s
Test Rust stable-x86_64-gnu on windows-latest	42s
Test Rust stable-i686-gnu on windows-latest	41s
Test Rust stable-i686-msvc on windows-latest	47s
Test Rust nightly on ubuntu-latest	22s
	19m 45s

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