Switch from dynamic to static requirements

[tekktrik]

We could upgrade all the libraries to switch from requirements.txt and optional-requirements.txt to defining them full inside pyproject.toml. I think the actual change implementation isn't too bad through Adabot's extended tooling.

Main concerns are that:

• The current way dependencies are defined is incredibly readable right now
• Existing documentation or guides may explicitly say to download requirements using the file (i.e. pip install -r requirements.txt)
• Existing projects such as the screenshot tool or circup may explicitly look at requirements.txt for requirements.

Happy to do this myself and look into the above before making a final suggestion or recommendation about how viable this is.