Fix test failures caused by type hint changes

- Use TYPE_CHECKING guard in recipes.py to prevent typing imports from
  appearing in module namespace (fixes test_recipes_are_documented)
- Update test_convert_help to check for function names with type hints
  in a more flexible way

sqlite_utils/recipes.py

@@ -1,4 +1,9 @@
-from typing import Any, Callable, Optional
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from typing import Any, Callable, Optional
 
 from dateutil import parser
 import json