fix(kad,mdns,misc): ensure instant is used instead of std::time

[zvolin]

Description

std::time is not implemented on platforms like browser wasm and it's usage fails with a runtime error.
This ensures that instant is used everywhere as it is compatible with wasm environments.

Notes & open questions

Change checklist

• 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

[dariusc93]

mdns would not be compatible with wasm, and for kad, please see #5347

EDIT: To clarify on mdns: it seems to rely on native sockets for its implementation. Not to say that this may change in the future to adapt for other implementation (if mdns is available on the browser beside discovering printers). May not be worth making the change there.

[zvolin]

closing in favor of #5347 then