refactor: client Entry with methods to read content

[Frando]

Description

This adds a iroh::client::Entry struct which wraps the iroh_sync::Entry and adds methods to read the content of the entry. Reading the entry needs a reference to either a Doc<C> or the Iroh<C> client (both work equally).

@flub mentioned that this is missing from the expected API. I started this at the hack session but didn't get very far but now it's in a good shape IMO.

Notes & open questions

Change checklist

• Self-review.
• Documentation updates if relevant.

[dignifiedquire]

why not store the client on the Entry?

[Frando]

why not store the client on the Entry?

That's what I did first. It makes the Entry generic over C: ServiceConnection<ProviderService>. And because it holds an RpcClient<C> it also cannot implement Deserialize. It would also make the LiveEvent generic over C and also not deserializable. So I thought to maybe stop making everything generic at that level, because LiveEvent<C> felt wrong. We could do two Entry structs, e.g. EntryClient and Entry or so, but to me the version with passing a client into the methods seems simpler. Open to other thoughts though!

[dignifiedquire]

yeah that makes sense, this api is nice enough :)