Fix type hints for TestReport.when and TestReport.location (#13345)

These are set in `TestReport.__init__` but weren't being picked up by
type checkers because of the annotations on `BaseReport`.

Fixes #12941.

Author: rouge8

changelog/13345.bugfix.rst

@@ -0,0 +1 @@
+Fix type hints for :attr:`pytest.TestReport.when` and :attr:`pytest.TestReport.location`.

src/_pytest/reports.py

@@ -260,6 +260,9 @@ class TestReport(BaseReport):
     """
 
     __test__ = False
+
+    when: Literal["setup", "call", "teardown"]
+    location: tuple[str, int | None, str]
     # Defined by skipping plugin.
     # xfail reason if xfailed, otherwise not defined. Use hasattr to distinguish.
     wasxfail: str