Code cleanup and number frames based on their location in the source video

[lizardgai4]

Most of the changes can be replicated by running the following two commands:
python -m black ./*.py
python -m isort ./*.py

The only other changes are in stammer.py, and they are:

• How frames are numbered and cleaning up the method of reverse enumeration
• Prevent a rare error where line breaks appear in a frame count string from ffmpeg

[Firepal]

Heads up; I'm in the process of splitting up logic into functions and making misc. changes in stammer.py to help me understand this repo I've inherited from ArdenButterfield. This might create quite a merge conflict with this PR.

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I sorta like what this does to some of the difficult-to-parse audio matching and video output code. Not a fan of how ffmpeg arguments each have a single line though. Makes it hard to read. We probably should've been using shutil.split...

Btw, this PR is still using long_modulators branch, and something is confusing the GitHub "Rebase and merge" logic with that branch's commit history.
It's considered good form to make a new branch based on main, and then make a PR from that.

[lizardgai4]

Okay, I can put these changes into my main branch and redirect this PR to pull from my main

EDIT: I can't change the base branch here. I would have to make a new PR to do it, so I'll keep it as is

EDIT 2: I removed most of Black's changes to stammer.py to avoid most merge conflicts