Move mux functionality into CondSwap chip #202

Job	Run time
Book tests	1m 24s
Build target wasm32-unknown-unknown	1m 45s
Bitrot check	1m 33s
Build target wasm32-wasi	1m 39s
Intra-doc links	1m 30s
Rustfmt	15s
Test on ubuntu-latest	7m 14s
Test on i686-unknown-linux-gnu	12m 59s
Test on windows-latest	9m 40s
Test on i686-unknown-linux-gnu with beta features	13m 15s
Test on macOS-latest	17m 28s
Test on ubuntu-latest with beta features	7m 22s
Test on i686-unknown-linux-gnu with nightly features	15m 38s
Test on windows-latest with beta features	9m 34s
Test on macOS-latest with beta features	13m 28s
Test on ubuntu-latest with nightly features	8m 26s
Test on windows-latest with nightly features	10m 49s
Test on macOS-latest with nightly features	13m 7s
	2h 27m 6s

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