fix(terminal): show teardown phase for xfail reports

[royy92]

What

Updates the short test summary for xfail reports from the teardown phase to include the phase in the output.
Previously, when both the test call and fixture teardown failed under an xfail marker, both reports were displayed identically:

XFAIL test_case.py::test_func
XFAIL test_case.py::test_func

After this change:

XFAIL test_case.py::test_func
XFAIL at teardown of test_case.py::test_func

Why

When an xfail-marked test produces reports from both the call and teardown phases, the short test summary does not indicate which report came from teardown.
This makes the two reports appear duplicated even though they represent failures from different test phases.

How

The xfail short-summary formatting now checks the report phase and adds at teardown of for teardown reports.
The existing output for call-phase xfail reports remains unchanged.

Tests

Added a regression test covering an xfail-marked test where both the test call and fixture teardown raise exceptions.
Also verified:

pytest testing/test_skipping.py -q
93 passed

pytest testing/test_terminal.py -q
220 passed, 9 skipped

pre-commit run --all-files also passes.

Closes #6997

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