Re-organize directory structure (#4971)

See discussion in #2491

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

stdlib/zoneinfo/__init__.pyi

@@ -0,0 +1,32 @@
+import os
+import typing
+from datetime import tzinfo
+from typing import Any, AnyStr, Iterable, Optional, Protocol, Sequence, Set, Type, Union
+
+_T = typing.TypeVar("_T", bound="ZoneInfo")
+
+class _IOBytes(Protocol):
+    def read(self, __size: int) -> bytes: ...
+    def seek(self, __size: int, __whence: int = ...) -> Any: ...
+
+class ZoneInfo(tzinfo):
+    @property
+    def key(self) -> str: ...
+    def __init__(self, key: str) -> None: ...
+    @classmethod
+    def no_cache(cls: Type[_T], key: str) -> _T: ...
+    @classmethod
+    def from_file(cls: Type[_T], __fobj: _IOBytes, key: Optional[str] = ...) -> _T: ...
+    @classmethod
+    def clear_cache(cls, *, only_keys: Iterable[str] = ...) -> None: ...
+
+# Note: Both here and in clear_cache, the types allow the use of `str` where
+# a sequence of strings is required. This should be remedied if a solution
+# to this typing bug is found: https://github.com/python/typing/issues/256
+def reset_tzpath(to: Optional[Sequence[Union[os.PathLike[AnyStr], str]]] = ...) -> None: ...
+def available_timezones() -> Set[str]: ...
+
+TZPATH: Sequence[str]
+
+class ZoneInfoNotFoundError(KeyError): ...
+class InvalidTZPathWarning(RuntimeWarning): ...