Fix class methods being excluded from the Python API docs

All class methods were excluded which makes sense for methods such
as poll, draw ... etc. however this would also exclude utility methods
that aren't associated with RNA classes.

The following methods for `bpy.types` classes are now included:

- Macro.define
- UI_UL_list.sort_items_by_name
- {Header/Menu/Panel/UIList}.{append/prepend/remove/is_extended}

doc/python_api/sphinx_doc_gen.py

@@ -768,13 +768,38 @@ def write_indented_lines(ident, fn, text, strip=True):
             fn(ident + l + "\n")
 
 
+def pyfunc_is_inherited_method(py_func, identifier):
+    assert type(py_func) == MethodType
+    # Exclude Mix-in classes (after the first), because these don't get their own documentation.
+    cls = py_func.__self__
+    if (py_func_base := getattr(cls.__base__, identifier, None)) is not None:
+        if type(py_func_base) == MethodType:
+            if py_func.__func__ == py_func_base.__func__:
+                return True
+        elif type(py_func_base) == bpy.types.bpy_func:
+            return True
+    return False
+
+
 def pyfunc2sphinx(ident, fw, module_name, type_name, identifier, py_func, is_class=True):
     """
     function or class method to sphinx
     """
 
     if type(py_func) == MethodType:
-        return
+        # Including methods means every operators "poll" function for e.g.
+        # would be listed in documentation which isn't useful.
+        #
+        # However excluding all of them is also incorrect as it means class methods defined
+        # in `bpy_types.py` for e.g. are excluded, making some utility functions entirely hidden.
+        if (bl_rna := getattr(py_func.__self__, "bl_rna", None)) is not None:
+            if bl_rna.functions.get(identifier) is not None:
+                return
+        del bl_rna
+
+        # Only inline the method if it's not inherited from another class.
+        if pyfunc_is_inherited_method(py_func, identifier):
+            return
 
     arg_str = str(inspect.signature(py_func))
 
@@ -789,7 +814,10 @@ def pyfunc2sphinx(ident, fw, module_name, type_name, identifier, py_func, is_cla
         arg_str = "()" if (arg_str == "(cls)") else ("(" + arg_str[6:])
         func_type = "classmethod"
     else:
-        func_type = "staticmethod"
+        if type(py_func) == MethodType:
+            func_type = "classmethod"
+        else:
+            func_type = "staticmethod"
 
     doc = py_func.__doc__
     if (not doc) or (not doc.startswith(".. {:s}:: ".format(func_type))):