tendermint: PrivateKey and PublicKey have From impls for ed25519-consensus types

[cratelyn]

currently, when working with tendermint::{PrivateKey, PublicKey}, users of the ed25519-consensus crate must convert a ed25519_consensus::VerificationKey or ed25519_consensus::SigningKey via TryFrom<&'_ [u8]>. this has the unfortunate effect of requiring a bounds check, on a value that is already known to be a valid key.

tendermint::PublicKey::from_raw_ed25519(&vk.to_bytes()).expect("consensus key is valid")

this branch introduces some additional From<T> implementations, to facilitate free conversions from ed25519-consensus types.

• 649dd37 tendermint: PrivateKey is From<ed25519_consensus::SigningKey>
• 4f1a95a tendermint: SigningKey is From<ed25519_consensus::SigningKey>
• ad24ea5 tendermint: PublicKey is From<ed25519_consensus::VerificationKey>
• 8769244 tendermint: VerificationKey is From<ed25519_consensus::VerificationKey>

an internal SigningKey::new() constructor is also added, for the sake of consistency with VerificationKey::new(). this is optional, i'd be happy to back out of that change if it seems prudent.

some additional from_ed25519_consensus methods are provided, for cases where type inference might not suffice. these felt complimentary to existing methods like from_raw_ed25519, but are another optional change i'd be happy to back out of.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 11.53846% with 23 lines in your changes are missing coverage. Please review.

Project coverage is 59.3%. Comparing base (99ed0b9) to head (a1bce2c).

❗ Current head a1bce2c differs from pull request most recent head 34e0c13. Consider uploading reports for the commit 34e0c13 to get more accurate results

Files	Patch %	Lines
tendermint/src/private_key.rs	0.0%	10 Missing ⚠️
tendermint/src/crypto/ed25519/signing_key.rs	0.0%	6 Missing ⚠️
tendermint/src/public_key.rs	42.8%	4 Missing ⚠️
tendermint/src/crypto/ed25519/verification_key.rs	0.0%	3 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #1401     +/-   ##
=======================================
- Coverage   60.1%   59.3%   -0.8%     
=======================================
  Files        271     271             
  Lines      26221   26549    +328     
=======================================
- Hits       15768   15762      -6     
- Misses     10453   10787    +334     

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[romac]

Very nice, thanks! 💐