Assign tasks to workers

[gabegma]

Part of #521
Fixes #411

Description:

• The tests used to be flacky on the CI, but I after rebasing on all the changes, I'm not sure if that is still the case. It seems it's no longer the case given the amount of back and forth. Yay!!
• This allows the user to manually assign the GPU to worker 0, because this is where the pipeline and encoder will be loaded.

Here is the memory before and after the change.

Checklist:

You should check all boxes before the PR is ready. If a box does not apply, check it to acknowledge it.

• ISSUE NUMBER. You linked the issue number (Ex: Resolve #XXX).
• PRE-COMMIT. You ran pre-commit on all commits, or else, you
  ran pre-commit run --all-files at the end.
• USER CHANGES. The changes are added to CHANGELOG.md and the documentation, if they impact
  our users.
• DEV CHANGES.
  • Update the documentation if this PR changes how to develop/launch on the app.
  • Update the README files and our wiki for any big design decisions, if relevant.
  • Add unit tests, docstrings, typing and comments for complex sections.

[gabegma]

BTW - While investigating memory usage - I’m under the impression that we have some memory leakage issues with the saliency tasks. I added issue #549.

[JosephMarinier]

Awesome! Good job on the graphs and all the profiling. 👍