tests(iroh): Test sync with restarting node

[Frando]

Description

• Add test for resuming sync after a node restart
• Improve sync logging
• Return sync finished details over the RPC boundary

This adds a test with the following flow.

• Node 1: spawn, create doc, create ticket
• Node 2: join ticket, add entry a
• Node 1: wait until received a
• Node 1: shutdown
• Node 2: add entry b
• Node 1: restart
• Node 1: wait until received b
• Node 2: add entry c
• Node 1: wait until received c

Also adjusts the logging a bit to be more useful.

Notes & open questions

Change checklist

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

[Frando]

CI fails with:

thread 'sync_restart_node' panicked at iroh/tests/sync.rs:1240:9:
Failed to receive or match all events: Event didn't match any matcher: SyncFinished(SyncEvent { peer: PublicKey(icdmm64o2lmqfyxw), origin: Connect(DirectJoin), finished: SystemTime { tv_sec: 1712604867, tv_nsec: 127329051 }, started: SystemTime { tv_sec: 1712604857, tv_nsec: 111028780 }, result: Err("Failed to establish connection") })

edit: found it, it was only a missing insecure_skip_relay_cert_verify

[Frando]

The test passes now, it was just an oversight.

This PR has no real changes. It only adds a test, improves logging, and returns the sync finished details over the RPC boundary.