Remove bool from verify functions' result

[dr-orlovsky]

Alternative to #144

I think this approach is better / safer - but it certainly is more complex

[codecov]

Codecov Report

Attention: 11 lines in your changes are missing coverage. Please review.

Files	Coverage Δ
commit_verify/src/lib.rs	100.0% <ø> (ø)
commit_verify/src/convolve.rs	83.3% <83.3%> (-3.3%)	⬇️
commit_verify/src/embed.rs	96.5% <91.3%> (-1.2%)	⬇️
commit_verify/src/commit.rs	75.4% <53.3%> (-5.4%)	⬇️

📢 Thoughts on this report? Let us know!.

[cryptoquick]

I like that this is using richer error types. This will help us a lot to handle reissuance issues our users will run into.

[zoedberg]

ACK, I agree this is a better approach than #144