Test code should be formatted and linted the same as library code. This
is the first step of that, simply including ./lib/test to the folder
that the black formatter runs on.
When the `await RPC_MANAGER.rpcs.pop()` explodes,
the traceback is for `RPC_MANAGER.rpcs.pop()`, e.g.
```
error: Program failed with an unhandled exception:
Traceback (most recent call last):
File "/opt/hostedtoolcache/pulumi/3.43.1/x64/pulumi-language-python-exec", line 179, in <module>
loop.run_until_complete(coro)
File "/opt/hostedtoolcache/Python/3.10.9/x64/lib/python3.10/asyncio/base_events.py", line 649, in run_until_complete
return future.result()
File "[..]/venv/lib/python3.10/site-packages/pulumi/runtime/stack.py", line 126, in run_in_stack
await run_pulumi_func(lambda: Stack(func))
File "[..]/venv/lib/python3.10/site-packages/pulumi/runtime/stack.py", line 51, in run_pulumi_func
await wait_for_rpcs()
File "[..]/venv/lib/python3.10/site-packages/pulumi/runtime/stack.py", line 73, in wait_for_rpcs
await RPC_MANAGER.rpcs.pop()
RecursionError: maximum recursion depth exceeded
```
This isn't super helpful in debugging these errors.
RPC_MANAGER already tracks uncaught excpetions from such RPCs
but wait_for_rpcs doesn't account for these until aftewards.
This changes wait_for_rpcs to reproduce the original tracebacks
when it encounters errors in waiting for RPCs.
The included test verifies that the more helpful traceback is produced.
Refs #11887