refactor(examples): distributed-key-value-store identify and rendezvous

[P1R]

Description

Following on issue #4449 Refactor and cleanup on three examples: refactor: use tokio instead of async-std in the distributed-key-value-store example and remove unnecesary dependencies refactor: remove unnecesary dependencies rendezvous example (async-std) refactor: use tokio instead of async-std in the identify example and remove unnecesary dependencies

Notes & open questions

• in the distributed-key-value example is it ok to put "EOL"in the expect?
• in the rendezvous example there where unnecessary dependencies in the Cargo.toml (so as in the identify)

Change checklist

• Removed unecesary dependencies on examples/rendezvous/Cargo.toml and examples/identify/Cargo.toml

• Changed async-std for tokio in examples/distributed-key-value-store/Cargo.toml and examples/identify/Cargo.toml

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

[P1R]

Sure, I will rewrite pull request for each example I forgot to ask that but I had it in mind. Thanks.