work queue executor does not have type annotations

[btovar]

Describe the bug work queue executor does not have type annotations. This means that it always passes make mypy when testing the code, even when incorrect types are used.

To Reproduce

1. Checkout master branch commit 70d6f0f
2. Confirm that parsl/executors/workqueue/executor.py does not have type annotations.

Expected behavior All functions and methods in the executor should have type annotations.

Environment

• OS: all
• Python version: all
• Parsl version: at least from commit 70d6f0f, but much earlier.

Distributed Environment It is independent of the distributed environment.

[benclifford]

cross-reference #873 which is about putting @typeguard.typechecked annotations on any function call that directly faces a user