Solve the Conflicting implementation of the From<ed25519_dalek::ed25519::Error> for PasetoError

[abdihakim148]

This error happens when the v3_public features is enable in combination with all or any of these other features:

1. v1_public
2. v2_public
3. v3_public

**Why is this happening? **
i could not get to the exact cause of this error but this solves the error.
when the above 3 features are enabled, they also enable the ed25519_dalek feature crate. and the v3_public feature enables the p384 feature crate. When the Error macro of thiserror derive the From<p384::ecdsa::Error> for PasetoError it also seems to create an implementation of From<ed25519_dalek::ed25519::Error> for PasetoError. This also happens when I did manual implementation of both traits. I could not figure the root cause for this behavior. and the from macro on the RsaCipher error variant also results in an implementation of this trait which results in a conflict. So i have manually implemented the From<ed25519_dalek::ed25519::Error> for PasetoError under a feature that only allows it's compilation when the ed25519_dalek is enabled and p384 feature is disabled, and this solves the error and all the 81 tests are passing when all the features are enabled as expected.

[abdihakim148]

closes #48