Re-organize directory structure (#4971)

See discussion in #2491

Co-authored-by: Ivan Levkivskyi <ilevkivskyi@dropbox.com>

stubs/retry/METADATA.toml

@@ -0,0 +1,2 @@
+version = "0.1"
+python2 = true

stubs/retry/retry/__init__.pyi

@@ -0,0 +1 @@
+from .api import retry as retry

stubs/retry/retry/api.pyi

@@ -0,0 +1,28 @@
+from logging import Logger
+from typing import Any, Callable, Dict, Optional, Sequence, Tuple, Type, TypeVar, Union
+
+_T = TypeVar("_T", bound=Callable[..., Any])
+_Decorator = Callable[[_T], _T]
+_R = TypeVar("_R")
+
+def retry_call(
+    f: Callable[..., _R],
+    fargs: Optional[Sequence[Any]] = ...,
+    fkwargs: Optional[Dict[str, Any]] = ...,
+    exceptions: Union[Type[Exception], Tuple[Type[Exception], ...]] = ...,
+    tries: int = ...,
+    delay: float = ...,
+    max_delay: Optional[float] = ...,
+    backoff: float = ...,
+    jitter: Union[Tuple[float, float], float] = ...,
+    logger: Optional[Logger] = ...,
+) -> _R: ...
+def retry(
+    exceptions: Union[Type[Exception], Tuple[Type[Exception], ...]] = ...,
+    tries: int = ...,
+    delay: float = ...,
+    max_delay: Optional[float] = ...,
+    backoff: float = ...,
+    jitter: Union[Tuple[float, float], float] = ...,
+    logger: Optional[Logger] = ...,
+) -> _Decorator: ...