Re-organize directory structure (#4971)

See discussion in #2491

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

stdlib/pipes.pyi

@@ -0,0 +1,15 @@
+import os
+
+class Template:
+    def __init__(self) -> None: ...
+    def reset(self) -> None: ...
+    def clone(self) -> Template: ...
+    def debug(self, flag: bool) -> None: ...
+    def append(self, cmd: str, kind: str) -> None: ...
+    def prepend(self, cmd: str, kind: str) -> None: ...
+    def open(self, file: str, rw: str) -> os._wrap_close: ...
+    def copy(self, file: str, rw: str) -> os._wrap_close: ...
+
+# Not documented, but widely used.
+# Documented as shlex.quote since 3.3.
+def quote(s: str) -> str: ...