Build

Add Rust-Toolchain, refactor generics, typos/cleanup #571

Job	Run time
build-macos (aarch64-apple-darwin)	14m 23s
build (i686-linux-android)	8m 40s
build-macos (aarch64-apple-ios)	13m 4s
build (armv7-linux-androideabi)	8m 25s
build-macos (aarch64-apple-ios-sim)	10m 50s
kotlin	10m 46s
build (aarch64-linux-android)	11m 13s
swift	10m 48s
package-android	8s
package-swift	33s
	1h 28m 50s

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