alter the PyObjMixin to carry over typing information from Node

as PyObjMixin is always supposed to be mixed in the mro
before nodes.Node the behavior doesn't change,
but all the typing information carry over to help mypy.

extracted from #8037

changelog/8248.trivial.rst

@@ -0,0 +1 @@
+Internal Restructure: let python.PyObjMixing inherit from nodes.Node to carry over typing information.

src/_pytest/python.py

@@ -23,7 +23,6 @@ from typing import Optional
 from typing import Sequence
 from typing import Set
 from typing import Tuple
-from typing import Type
 from typing import TYPE_CHECKING
 from typing import Union
 
@@ -255,21 +254,14 @@ def pytest_pycollect_makeitem(collector: "PyCollector", name: str, obj: object):
             return res
 
 
-class PyobjMixin:
+class PyobjMixin(nodes.Node):
+    """this mix-in inherits from Node to carry over the typing information
+
+    as its intended to always mix in before a node
+    its position in the mro is unaffected"""
+
     _ALLOW_MARKERS = True
 
-    # Function and attributes that the mixin needs (for type-checking only).
-    if TYPE_CHECKING:
-        name: str = ""
-        parent: Optional[nodes.Node] = None
-        own_markers: List[Mark] = []
-
-        def getparent(self, cls: Type[nodes._NodeType]) -> Optional[nodes._NodeType]:
-            ...
-
-        def listchain(self) -> List[nodes.Node]:
-            ...
-
     @property
     def module(self):
         """Python module object this node was collected from (can be None)."""