fix: stabilize identify integration tests under parallel xdist load

[acul71]

Summary

• Harden identify handler to wait for listen addresses and fall back to transport addrs when advertising (libp2p/identity/identify/identify.py)
• Add test synchronization helpers and explicit _identify_peer waits for load-sensitive integration tests
• Split make test into parallel (-m "not serial_only") and serial phases for six flaky-under-load tests
• Register @pytest.mark.serial_only in pyproject.toml

Closes #1377

Root cause

Six identify/host/quic tests fail only under full-suite pytest -n auto (~3060 tests), not in isolation. Investigation notes were kept local under downloads/ (gitignored, not in the repo).

Not caused by #1372/#1374 logic changes; #1372 increased parallel suite load and exposed latent timing races.

Changed files

Area	Files
Production	libp2p/identity/identify/identify.py, libp2p/tools/utils.py
Tests	tests/utils/identify_test_helpers.py, identify/host/quic test files
Infra	Makefile, pyproject.toml, newsfragments/1377.bugfix.rst

Test plan

• make lint
• make typecheck
• make test (parallel + serial phases)
• make linux-docs
• pytest -n auto --timeout=1200 tests/core (CI tox parity — 2807 passed locally)
• Confirm 6 previously failing tests pass in serial phase

Notes for reviewers

• wait_for_peerstore_addrs added to libp2p/tools/utils.py but not wired into global connect() (caused suite-wide timeouts during investigation)
• Makefile split affects local make pr only; CI uses tox pytest -n auto tests/core, which passes with the production/test hardening alone

Made with Cursor

[sumanjeet0012]

@acul71 @seetadev

I created a fresh virtual environment, installed all dependencies, and ran the make pr command on macOS.

All tests passed successfully; however, I encountered the following runtime warnings:

1. During test execution:

[gw4] [ 98%] PASSED tests/interop/zig_libp2p/test_zig_basic.py::test_zig_libp2p_placeholder
/Users/sumanjeet/code/py-libp2p/.venv/lib/python3.10/site-packages/_pytest/unraisableexception.py:33:
RuntimeWarning: coroutine 'AsyncMockMixin._execute_mock_call' was never awaited
gc.collect()
RuntimeWarning: Enable tracemalloc to get the object allocation traceback

2. Warnings summary:

tests/core/transport/webrtc/test_connection.py::TestOpenStream::test_open_stream_increments_ids_by_2
tests/core/transport/webrtc/test_connection.py::TestOpenStream::test_open_stream_on_closed_connection_raises
tests/core/transport/webrtc/test_connection.py::TestClose::test_close_is_idempotent
/Users/sumanjeet/.local/share/uv/python/cpython-3.10.19-macos-aarch64-none/lib/python3.10/unittest/mock.py:2135:
RuntimeWarning: coroutine 'AsyncMockMixin._execute_mock_call' was never awaited
setattr(_type, entry, MagicProxy(entry, self))
Enable tracemalloc to get the object allocation traceback.
See https://docs.pytest.org/en/stable/how-to/capture-warnings.html#resource-warnings for more info.

Aside from these warnings, the test suite completed successfully.