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

• 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

[jxs]

Hi David, and thanks for this! Overall looks good to me, can we separate this PR into one for each example? Thanks!

[jxs]

can we keep std::futures::select! and therefore this fuse?

[P1R]

@jxs i did as just line following other example implementations with tokios as the following:
chat/src/main.rs:88: let mut stdin = io::BufReader::new(io::stdin()).lines();
ipfs-private/src/main.rs:172: let mut stdin = io::BufReader::new(io::stdin()).lines();

but I can try your approach later tonight.

[P1R]

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