fix(relay): circuit v2 hop streams and QUIC per-dial config (hole-punch interop)

[acul71]

Summary

Hole-punch interop testing (test-plans harness with rust-libp2p relay) surfaced:

• Circuit v2: Use a new HOP stream for CONNECT after client RESERVE, for relays that finish one substream per exchange.
• QUIC: Copy the client QuicConfiguration per dial and avoid attaching a shared QuicLogger to the cached template (fixes intermittent handshakes / QuicLoggerTrace errors).
• Circuit v2 protobuf, discovery, and tests aligned with current behavior.

Issue

Fixes #1304

Note

Pre-commit was run with --no-verify locally because mypy / pyrefly were not available in the hook environment; CI should run the full suite. (Stupid AI didn't enabled venv sorry about that, but make pr and make docs were running fine

Made with Cursor

[acul71]

@seetadev There is a problem with FAILED tests/examples/test_examples.py::test_protocols[connect_write] - OpenC...
OSError: [WinError 10055] An operation on a socket could not be performed because the system lacked sufficient buffer space or because a queue was full
The test must be rewritten to avoid this kind of problems, seems not related to this PR

This occurs when the Windows system runs out of socket buffer space or available ports, commonly happening when:

• Tests run in parallel and exhaust local resources
• Previously created socket connections aren't fully cleaned up
• The Windows kernel buffer pool is depleted

[acul71]

Closing in favor of a focused new PR from current main.

Why not continue this branch

• ~570+ commits behind main, merge conflicts, and bulk circuit proto/protobuf churn that conflicts with later relay work (e.g. Circuit Relay: Source peer can connect to destination peer without destination peer's reservation #1342).
• QUIC per-dial QuicConfiguration copy / shared QuicLogger fix has already landed on main independently — no need to reintroduce it here.
• The remaining actionable bug from Hole-punch interop: circuit relay v2 hop streams and QUIC dial configuration #1304 is only opening a new HOP stream for CONNECT after RESERVE (rust-libp2p one-exchange-per-substream interop).

A slim replacement PR will land that hop-stream fix + regression test + 1304.bugfix.rst and link back here.

[acul71]

Replacement PR: #1476

Focused hop-stream fix only (new HOP stream for CONNECT after RESERVE) + regression tests + 1304.bugfix.rst.