Review our protocols for how they close a connection

[flub]

We may be closing connections unreliably in our QUIC protocols. Review all our protocols:

• [x] iroh-docs: broken
  • Probably won't fix and migrate to willow proto instead
• [ ] iroh-blobs
• [ ] iroh-gossip
• [ ] iroh-doctor
• [x] iroh-willow
  • new impl has reliable shutdown coordination