Modernize CI somewhat #270

Job	Run time
Test on i686-unknown-linux-gnu (using cross)	1m 14s
Verify code formatting	14s
Test on armv7-linux-androideabi (using cross)	1m 24s
Test on aarch64-unknown-linux-gnu (using cross)	1m 10s
coverage	44s
Test on powerpc-unknown-linux-gnu (using cross)	1m 10s
Check warnings	14s
Test on powerpc64-unknown-linux-gnu (using cross)	1m 10s
Test Rust 1.60.0 on ubuntu-latest	1m 59s
Test Rust stable on ubuntu-latest	23s
Test Rust stable on macos-latest	23s
Test Rust stable on windows-latest	54s
Test Rust stable-i686-msvc on windows-latest	1m 16s
Test Rust beta on ubuntu-latest	25s
Test Rust nightly on ubuntu-latest	25s
	13m 5s

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