config: make `collect_ignore` accept any PathLike

The main reason is to remove a reference to `py.path`.

doc/en/reference/reference.rst

@@ -936,7 +936,7 @@ pytest treats some global variables in a special manner when defined in a test m
 **Tutorial**: :ref:`customizing-test-collection`
 
 Can be declared in *conftest.py files* to exclude test directories or modules.
-Needs to be ``list[str]``.
+Needs to be a list of paths (``str``, :class:`pathlib.Path` or any :class:`os.PathLike`).
 
 .. code-block:: python
 

src/_pytest/config/__init__.py

@@ -1445,9 +1445,7 @@ class Config:
         modpath = Path(mod.__file__).parent
         values: List[Path] = []
         for relroot in relroots:
-            if isinstance(relroot, Path):
+            if isinstance(relroot, os.PathLike):
-                pass
-            elif isinstance(relroot, LEGACY_PATH):
                 relroot = Path(relroot)
             else:
                 relroot = relroot.replace("/", os.sep)

testing/test_collection.py

@@ -367,12 +367,19 @@ class TestCustomConftests:
     def test_collectignore_exclude_on_option(self, pytester: Pytester) -> None:
         pytester.makeconftest(
             """
-            # potentially avoid dependency on pylib
-            from _pytest.compat import legacy_path
             from pathlib import Path
-            collect_ignore = [legacy_path('hello'), 'test_world.py', Path('bye')]
+
+            class MyPathLike:
+                def __init__(self, path):
+                    self.path = path
+                def __fspath__(self):
+                    return "path"
+
+            collect_ignore = [MyPathLike('hello'), 'test_world.py', Path('bye')]
+
             def pytest_addoption(parser):
                 parser.addoption("--XX", action="store_true", default=False)
+
             def pytest_configure(config):
                 if config.getvalue("XX"):
                     collect_ignore[:] = []