experimental: Add minimal rust backend. #413

Job	Run time
test-on-ubuntu (ubuntu-20.04, python3.8, gcc-11, g++-11, g++-11, "ppa:ubuntu-toolchain-r/test")	26m 34s
test-on-ubuntu (ubuntu-20.04, python3.9, gcc-11, g++-11, g++-11, "ppa:ubuntu-toolchain-r/test")	26m 10s
test-on-ubuntu (ubuntu-20.04, python3.10, gcc-11, g++-11, g++-11, "ppa:ubuntu-toolchain-r/test")	26m 23s
test-on-ubuntu (ubuntu-20.04, python3.11, gcc-11, g++-11, g++-11, "ppa:ubuntu-toolchain-r/test")	26m 47s
test-on-ubuntu (ubuntu-20.04, python3.12, gcc-11, g++-11, g++-11, "ppa:ubuntu-toolchain-r/test")	26m 46s
test-on-ubuntu (ubuntu-22.04, python3.8, gcc-11, g++-11, g++-11, "ppa:ubuntu-toolchain-r/test")	26m 52s
test-on-ubuntu (ubuntu-22.04, python3.9, gcc-11, g++-11, g++-11, "ppa:ubuntu-toolchain-r/test")	27m 55s
test-on-ubuntu (ubuntu-22.04, python3.10, gcc-11, g++-11, g++-11, "ppa:ubuntu-toolchain-r/test")	28m 46s
test-on-ubuntu (ubuntu-22.04, python3.11, gcc-11, g++-11, g++-11, "ppa:ubuntu-toolchain-r/test")	28m 28s
test-on-ubuntu (ubuntu-22.04, python3.12, gcc-11, g++-11, g++-11, "ppa:ubuntu-toolchain-r/test")	26m 47s
test-on-ubuntu (ubuntu-20.04, python3.8, gcc-5, g++-5, g++-5, "deb http://us.archive.ubuntu.com/u...	25m 31s
test-on-ubuntu (ubuntu-20.04, python3.8, clang-7, clang++-7, clang-7)	27m 0s
test-on-ubuntu (ubuntu-22.04, python3.10, clang-15, clang++-15, clang-15)	27m 59s
	5h 51m 58s

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