Fix runner setup order for async tests

[deepakganesh78]

Fixes #818

Reproduction

A synchronous fixture can monkeypatch event-loop creation state before pytest-asyncio creates its runner for an async test. The added regression test simulates the reported pytest-mock/socket lifecycle problem by replacing pytest_asyncio.plugin.Runner from a sync fixture; on main, the runner is constructed while the fixture is active and the test errors.

Root cause

PytestAsyncioFunction.setup() appended the scoped runner fixture to the end of fixturenames. Pytest therefore set up user fixtures first and set up/teared down the runner inside those fixtures' lifetime.

Fix

Insert the runner fixture at the front of fixturenames so the event loop runner encompasses synchronous fixtures used by async tests. This preserves normal async test behavior while preventing user fixture monkeypatching from interfering with event loop creation.

Compatibility notes

This only changes fixture ordering for pytest-asyncio's internal runner fixture. No public API or configuration changes are introduced.

Validation

• python -m pytest tests/test_set_event_loop.py::test_runner_encompasses_sync_fixtures -q: 1 passed.
• Regression check with the fix reverted: tests/test_set_event_loop.py::test_runner_encompasses_sync_fixtures failed with RuntimeError: Runner constructed while user fixture is active.
• python -m pytest tests/test_set_event_loop.py -q: 61 passed, 1 failed. The failure is pre-existing on this Windows/Python 3.13 + pytest 9.1.1 environment: test_asyncio_run_after_async_fixture_does_not_leak_loop errors with PytestAssertRewriteWarning: Module already imported so cannot be rewritten; pytest_asyncio and reproduces with the runner-order fix reverted.
• python -m pytest: 290 passed, 3 skipped, 6 failed. The failures are the same pre-existing Windows/Python 3.13 + pytest 9.1.1 subprocess/in-process loop/assert-rewrite failures and are unrelated to this change.
• pre-commit run --files pytest_asyncio/plugin.py tests/test_set_event_loop.py changelog.d/818.fixed.rst: passed.

[tjkuson]

I've moved the PR to draft as tests are failing. You are welcome to re-open the PR if you manage to get a solution with passing tests.