The condition was accidentally reversed during refactoring in
9730ac4c5691c36d58c06deec1762a4831b268c5 . It would result in skipped
tests on builds with proper support and false negatives on builds
without proper feature support.
Credit for reporting the issue and the fix goes to Stanislav Levin.
Avoid using the environment variables for feature detection and use the
feature-test utility instead.
Remove the obsolete environment variables from conf.sh, since they're no
longer used anywhere.
The ability to conveniently mark tests which should only be run when the
CI_ENABLE_ALL_TESTS environment variable is set seems to be useful on a
general level and therefore it should not be limited to the "timeouts"
system test, where it is currently used.
pytest documentation [1] suggests to reuse commonly used test markers by
putting them all in a single Python module which then has to be imported
by test files that want to use the markers defined therein. Follow that
advice by creating a new bin/tests/system/pytest_custom_markers.py
Python module containing the relevant marker definitions.
Note that "import pytest_custom_markers" works from a test-specific
subdirectory because pytest modifies sys.path so that it contains the
paths to all parent directories containing a conftest.py file (and
bin/tests/system/ is one). PyLint does not like that, though, so add a
relevant PyLint suppression.
The above changes make bin/tests/system/timeouts/conftest.py redundant,
so remove it.
[1] https://docs.pytest.org/en/7.0.x/how-to/skipping.html#id1
