add halo2_gadgets_optimized #261

Job	Run time
Test on ubuntu-latest	10m 48s
Test on windows-latest	15m 28s
Test on macOS-latest	10m 9s
Book tests	1m 35s
Test on ubuntu-latest with beta features	10m 41s
Build target wasm32-unknown-unknown	1m 59s
Bitrot check	1m 41s
Build target wasm32-wasi	2m 0s
Test on windows-latest with beta features	15m 24s
Test on macOS-latest with beta features	9m 39s
Code coverage	21m 27s
Test on ubuntu-latest with nightly features	12m 45s
Test on i686-unknown-linux-gnu	22m 55s
Test on windows-latest with nightly features	18m 21s
Test on i686-unknown-linux-gnu with beta features	22m 41s
Test on macOS-latest with nightly features	10m 55s
Intra-doc links	1m 26s
Test on i686-unknown-linux-gnu with nightly features	27m 53s
Rustfmt	17s
	3h 38m 4s

Provide feedback