pytest 9.1.0: conftest.py `addoption` regressed in nested directories

[manupillai308]

For a directory like below:

|- A
   |- conftest.py
|- B
   |- conftest.py (<== we have addoption here)

When we invoke the test from directory A, the CLI args added through addoption in B/conftest.py was loaded correctly.
The new version seems to fail here.
It throwspytest: error: unrecognized arguments: <args-list>

pytest: 9.1.0
OS: Ubuntu 24.04

• a detailed description of the bug or problem you are having
• output of pip list from the virtual environment you are using
• pytest and operating system versions
• minimal example if possible

[bluetech]

Please show the following:

• Your pytest configuration
• Your exact pytest invocation
• Output of pytest --collect-only

[chrisburr]

I've also ran into this and have a prepared a reproducer/fix in #14622