Add operators &, |, ! for Tracer<Bit>

[voltrevo]

Enables you to write eg:

let a = builder.add_input::<bool>();
let b = builder.add_input::<bool>();
let a_or_b = a | b; // Same as `!(!a & !b)`

I wanted these ops when I made a circuit for Rock Paper Scissors Lizard Spock.

[voltrevo]

So that .to_inner().nodes()[0] could be replaced with .node(), otherwise repeated many times now.

[voltrevo]

The RefMut only lives to the end of the method and the state isn't used before then, so there's no need to explicitly drop it.

[sinui0]

Nice, thank you!

[sinui0]

@voltrevo looks like you just need to run fmt

[voltrevo]

@voltrevo looks like you just need to run fmt

Done :)