(wip) feat(iroh-sync): Inline small content

[Frando]

Description

WIP - Fixes #2141

• Refactor interface between iroh-sync and a content store, use a trait instead of arc'ed callbacks
• Inline small content (< 1024 bytes) during set reconciliation and in gossip messages
• Store incoming inlined content in the content store

Notes & open questions

• I updated the sync_full_basic test as a smoke test. Most other integration tests are still broken because we don't emit ContentReady events if the content is already available (marked as Complete ) in the RemoteInsert event. ContentReady is only emitted if the content is not yet available at the time when the RemoteInsert is emitted.

Change checklist

• [ ] Self-review.
• [ ] Documentation updates if relevant.
• [ ] Tests if relevant.