refactor(peer-store): single behavior Event

[elenaf9]

Description

Refactor the events emitted by the peer_store::Behavior:

1. Merge the current 3 event types (behavior::Event, store::Event, memory_store::Event) into a single type that is emitted by the Store implementation.
2. Use more descriptive event variants AddressAdded, AddressRemoved that also expose the specific Multiaddr.
3. Remove Event::CustomDataUpdate variant.

Discussed in #5926 (comment) and #5926 (comment).

Notes & open questions

I've removed the Event::CustomDataUpdate because I don't think it makes sense to emit an event for a synchronous, user-triggered operation. It doesn't give any information that the user doesn't already know.
For the user-triggered adding and removal of addresses, however, I am still emitting events so that it is consistent with the swarm-triggered change of addresses. @dknopik @drHuangMHT do you agree with this?

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

[dknopik]

I feel like these changes make sense. 👍

[drHuangMHT]

LGTM! This significantly improves ergonomics!

[jxs]

Thanks for this Elena! And Daniel and DrHuang for the review!