Fix junitxml count for teardown errors

[puneetdixit200]

Fixes #3850

Summary

• correct the JUnit XML tests count when a test passes during call but fails during teardown
• assert in run_and_parse that the testsuite tests attribute matches the emitted <testcase> nodes
• keep call-failure plus teardown-error as separate testcase nodes, while the pass-plus-teardown-error path stays one testcase node
• add a changelog entry

Tests

• .venv/bin/python -m pytest testing/test_junitxml.py -q
• .venv/bin/pre-commit run --color never --files src/_pytest/junitxml.py testing/test_junitxml.py changelog/3850.bugfix.rst
• git diff --check

AI assistance was used while iterating on the patch and tests. I reviewed the change and can explain it.

[nicoddemus]

Thanks, left some comments!

[puneetdixit200]

Rebased onto current main to pick up the unittest skip fixture fix from #14505.

Verification run locally:

uv run --with-editable . --extra dev python -m pytest testing/test_junitxml.py testing/test_unittest.py::test_setup_inheritance_skipping testing/test_unittest.py::test_pdb_teardown_skipped_for_classes testing/test_debugging.py::TestPDB::test_pdb_unittest_skip -q --junitxml=/tmp/pytest-14501-after-rebase.xml
# 142 passed, 3 skipped

[puneetdixit200]

The current head addresses the review comments:

• the new JUnit XML cases now go through run_and_parse
• run_and_parse asserts the tests attribute against the emitted <testcase> nodes
• the production branch has a comment pointing back to junit xml "tests" number seems wrong if only teardown fails #3850
• the branch was rebased onto current main to pick up the unittest skip fixture fix

Latest local check after the rebase was 142 passed, 3 skipped for testing/test_junitxml.py plus the related unittest/debugging skip tests.

[nicoddemus]

Thanks!