Add stubtest test for property aliases

Author: hamdanal

mypy/test/teststubtest.py

@@ -850,11 +850,13 @@ def test_property(self) -> Iterator[Case]:
             class Good:
                 @property
                 def read_only_attr(self) -> int: ...
+                read_only_attr_alias = read_only_attr
             """,
             runtime="""
             class Good:
                 @property
                 def read_only_attr(self): return 1
+                read_only_attr_alias = read_only_attr
             """,
             error=None,
         )