Bug/regression: Ancestor conftest inclusion

[thejcannon]

👋 (I searched conftest in the issues, closed and open, and didn't find a relevant issue)

🐞 bug report

Affected Rule

The issue is caused by the rule: `py_test` (and `py_library`) (and Gazelle)

Is this a regression?

Kinda yes, kinda no? The previous version in which this bug was not present was: 1.5.4 (pre 1.6.X)

Description

I'm having some heartburn updating past 1.6.0 due to #2998 (I'll probably dump those in another issue), but one that sticks out is how Gazelle handles (or doesn't handle) ancestor conftest.py.

(See the repro for code structure)

• Pytest loads ancestor conftest.py files (not just the ones in the test file's directory). See the docs
• Old Gazelle rules had all the test targets in the tests/ dir, meaning they got the :conftest dependency (even if they were in descendant directories)
• New Gazelle rules have the test in the test's parent directory (this is a good thing 👍) but now those targets no longer get the automatic ancestor conftest dependency

🔬 Minimal Reproduction

Given this structure (all files empty, except for projects/repro/BUILD.bazel which has # gazelle:python_root)

<root>/
└── projects/
    └── repro/
        ├── BUILD.bazel
        └── tests/
            ├── BUILD.bazel
            ├── conftest.py
            ├── test_root_dir.py
            └── subdir/
                └── test_subdir.py

• On 1.5.4: Gazelle will put everything in projects/example/tests/BUILD.bazel, where specifically test_subdir.py has a dependency on :conftest
• On 1.6.0: Gazelle puts conftest.py and test_root_dir.py targets in projects/example/tests/BUILD.bazel (with the test depending on :conftest) but projects/example/tests/subdir:test_subdir doesn't depend on conftest.py anymore)

🔥 Exception or Error

(If you put fixtures/hooks in conftest.py, especially ones with automagically execute, they won't work)

🌍 Your Environment

N/A

Rules_python version:

1.6.3

Anything else relevant?