Redesign `RecordStore` API / interaction

Description

Currently, RecordStore trait returns Result only for put and add_provider operations. However, custom implementations (for example DB-based) could return errors on each operation.

I wonder whether it's possible to change this trait and add Result on each operation to make the trait more consistent with use cases.

Motivation

This change will allow handling errors for implementations in an idiomatic way.

Current Implementation

    /// Gets a record from the store, given its key.
    fn get(&'a self, k: &Key) -> Option<Cow<'_, Record>>;

    /// Puts a record into the store.
    fn put(&'a mut self, r: Record) -> Result<()>;

    /// Removes the record with the given key from the store.
    fn remove(&'a mut self, k: &Key);

    /// Gets an iterator over all (value-) records currently stored.
    fn records(&'a self) -> Self::RecordsIter;

.....

Are you planning to do it yourself in a pull request?

Not this time. This change could affect inner Kademlia error handling.

Locate the RecordStore trait and inspect its current operations and the inner Kademlia error-handling paths that depend on it. Determine which operations need Result returns and assess the impact on custom implementations and callers; done requires an agreed API redesign with consistent error propagation.