feat: impl Deref for PublicKey

[varun-doshi]

Description

Fixes #3437
Implement Deref::[u8,32] for PublicKey and SecretKey

Change checklist

• Self-review.

[dignifiedquire]

We shouldn't do this for SecretKey, it is too risky given it is secret material

[varun-doshi]

We shouldn't do this for SecretKey, it is too risky given it is secret material

Understood, changes made

[rklaehn]

We shouldn't do this for SecretKey, it is too risky given it is secret material

I am not so sure about this. SecretKey has to_bytes, so it's not like the bytes are hidden. I can see why you don't want to implement Display for SecretKey, but Deref seems pretty harmless.

Nevertheless the place where I find the Deref really useful is the PublicKey/NodeId, so I agree that doing it for SecretKey is not necessary. But it seems that if you have one way to get the bytes adding another slightly more convenient way isn't really bad for security.