refactor(kad): Add Key to InboundRequest::{AddProvider, PutRecord}.

[dariusc93]

Description

This PR introduces Key to InboundRequest::AddProvider and InboundRequest::PutRecord to provide the record key when it is inserted into the RecordStore.

Resolves #6048.

Notes & open questions

While one could just enable filtering, check the record for the key and then insert it into the store, I do feel this would provide information without requiring one to enable filtering and be responsible for inserting into the store.

Question:

1. Should we instead have it as Option<Key> so when if filtering is enabled, the field would return None and with it being . disabled, it would return Some(_)?

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