migrate later to new pyre architecture

Summary:
We're migrating fbcode to use  Pyre's new architecture.

To type check your project:

```
arc pyre check //buck/pattern/...
```

You can enable this by adding `typing = True` to individual buck targets OR

```
# in a PACKAGE file
load("fbcode_macros//build_defs:python.bzl", "python")
python.set_typing(True)
```
will type check all buck targets nested underneath.

This diff removes the configuration and replaces it with our new buck based architecture and silences any resulting errors.

Reviewed By: fried

Differential Revision: D64200949

fbshipit-source-id: e4416a636aa45872a2f5bbf7ba6d5d0aeffcc9cc

later/tests/test_task.py

@@ -286,6 +286,7 @@ async def test_watcher_START_TASK_with_working_fixer(self) -> None:
     async def test_watcher_canceled_parent_aexit(self) -> None:
         loop = asyncio.get_running_loop()
         task: asyncio.Task = loop.create_task(asyncio.sleep(500))
+        # pyre-fixme[16]: Module `builtins` has no attribute `TimeoutError`.
         with self.assertRaises(asyncio.TimeoutError):
             async with later.timeout(0.2):
                 async with later.Watcher() as watcher: