Retain tmp paths for setup and teardown errors

[GruffElixir]

Fixes #14998.

tmp_path_retention_policy = "failed" currently removes a temporary directory before setup or teardown outcomes are known. This loses debugging evidence for fixture setup errors and teardown errors.

This change defers the retention decision until the teardown report is available. Setup skips keep the existing cleanup behavior from #10502, while setup errors, call failures, and teardown errors retain their directories.

Tests:

• uv run --frozen pytest testing/test_tmpdir.py -q (49 passed, 11 skipped)
• uvx --from ruff ruff check src/_pytest/tmpdir.py testing/test_tmpdir.py
• uvx --from ruff ruff format --check src/_pytest/tmpdir.py testing/test_tmpdir.py
• Full suite: 4450 passed, 157 skipped, 14 xfailed, 1 xpassed; one unrelated failure in testing/acceptance_test.py::TestInvocationVariants::test_pydoc due to Windows/Python 3.14 UTF-8 decoding.
• git diff --check

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[Str0k]

I found a regression in the setup-skip path: removing tmp_path from
pytest_runtest_makereport can run before dependent fixtures finish teardown.
A fixture that accesses its temporary files after yield then raises
FileNotFoundError, turning a skipped test into a teardown error.

Minimal reproduction, run with -o tmp_path_retention_policy=failed:

import pytest


@pytest.fixture
def resource(tmp_path):
    (tmp_path / "input.txt").write_text("fixture data", encoding="utf-8")
    yield tmp_path
    assert (tmp_path / "input.txt").read_text(encoding="utf-8") == "fixture data"


@pytest.fixture
def unavailable(resource):
    pytest.skip("optional service unavailable")


def test_optional_service(unavailable):
    pass

The base commit 3fd8675 reports 1 skipped; PR head ca34872 reports
1 skipped, 1 error on Python 3.12. Could cleanup for setup skips be deferred
until dependent fixture teardown completes? This would also make a useful
regression test alongside the setup/teardown error cases.

Disclosure: Codex assisted with identifying and reproducing this case.

[GruffElixir]

Thanks for the repro. I reproduced the setup-skip teardown case and pushed 890f4ce to this PR. Cleanup now waits for the final teardown report, so dependent fixtures can still use tmp_path; teardown errors still keep the directory. The tmpdir suite is 50 passed, 11 skipped, and Ruff is clean.