fix(identity): add From & Into for public keys

[DougAnderson444]

Description

This patch removes the version 0.2.0 for deprecations as libp2p-identity is only at 0.1.1 and this can be confusing to the reader.

It also adds impl From<ed25519::PublicKey> for PublicKey (et al.) so that PublicKey::from(ed25519::PublicKey) works.

Fixes #3802.

Notes & open questions

Change checklist

• I have performed a self-review of my own code
• I have made corresponding changes to the documentation (deprecation notices)
• I have added tests that prove my fix is effective or that my feature works rsa
• A changelog entry has been made in the appropriate crates

[thomaseizinger]

Thanks for sending this!

Direction looks good, I left some inline comments :)

[thomaseizinger]

FYI: I slightly revised your description to make a better commit message once we merge this :)

[DougAnderson444]

FYI: I slightly revised your description to make a better commit message once we merge this :)

Thank you, I had the hardest time with this title 😆

[thomaseizinger]

Thanks for incorporating the comments :)

[thomaseizinger]

Thanks for your patience and incorporating the comments :)

[DougAnderson444]

Thanks for your patience and incorporating the comments :)

and thank you for your reviews and suggestions @thomaseizinger! Learning more about rust-libp2p in 3 days than I could even imagine.