Move mux functionality into CondSwap chip #210

Job	Run time
Bitrot check	1m 32s
Book tests	3m 38s
Build target wasm32-unknown-unknown	3m 58s
Build target wasm32-wasi	3m 54s
Intra-doc links	3m 35s
Rustfmt	14s
Test on ubuntu-latest	9m 23s
Test on i686-unknown-linux-gnu	15m 25s
Test on windows-latest	12m 14s
Test on i686-unknown-linux-gnu with beta features	15m 50s
Test on macOS-latest	10m 7s
Test on i686-unknown-linux-gnu with nightly features	17m 37s
Test on ubuntu-latest with beta features	8m 59s
Test on windows-latest with beta features	12m 4s
Test on macOS-latest with beta features	11m 43s
Test on ubuntu-latest with nightly features	10m 28s
Test on windows-latest with nightly features	13m 46s
Test on macOS-latest with nightly features	11m 30s
	2h 45m 57s

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