Add cSHAKE128 and cSHAKE256 implementations

[elichai]

A few notes about the implementation:

1. I left the code for changing the function name (N) commented out, I can either remove it, or leave it with an empty function name (although that might degrade the performance a little bit).
2. I added another Sha3State so CSHAKE can implement Reset without allocating the customization string. but because of that I couldn't use the state macro.
3. I added a has_customization boolean that if it's not it makes it the same as SHAKE.
4. I had to copy some logic from digest::dev because nothing there could support a hash function that doesn't implement Default (We could prob extend xof_test to accept a constructor, but we'll need a different new_test! macro that will support Blob3 and know to call new on the hasher with the customization)

The test vectors are from https://github.com/damaki/libkeccak/tree/master/tests/kat/testvectors/cSHAKE together with the current SHAKE tests for an empty customization.

[elichai]

I'm starting to think it might be better to remove the Reset implementation so that not everyone will need to pay for that extra State just for the few people that actually use it.

[newpavlov]

Sorry for the late reply! Can you please rebase and update the code to digest v0.10?

[elichai]

Superceeded by #355