fix dependency issues and rustc warnings

[reject-i]

###Description

• Remove unused dependencies:
  • aleph-bft-crypto: async-trait, tokio
  • aleph-bft-examples-blockchain: sha3, unsigned-varint
• Remove ineffective #[must_use] attributes from trait methods
• Set workspace resolver to "2" to match edition 2021

All tests continue to pass. Verified with cargo +nightly udeps.

[github-actions[bot]]

Please make sure the following happened

• [ ] Appropriate tests created
• [ ] Infrastructure updated accordingly
• [ ] Updated existing documentation
• [ ] New documentation created
• [ ] Version bumped if breaking changes

[reject-i]

Marcin-Radecki Hi ! check pls , thanks