[WIP] refactor: app state + widget refactor

[ClementTsang]

Description

A description of the change and what it does. If relevant (such as any change that modifies the UI), please provide screenshots of the change:

Rather large and long-awaited refactoring of application state to not be as bloated and/or hard to develop for.

Main goals:

• Shift GUI element state away from main app state, should be stored within the element
• Maybe look into rewriting how GUI is laid out + stored in state to reduce stuff like widgets.get_mut(blah blah blah...), that gets real tiring real quick.
• This may also require refactoring/rewriting how we do element layouts and event handling.

Current ideas/thoughts on implementation:

• Most of the current app state is actually fine. Storing things like collected data, converted data, if we're in dd - these are all valid things to store in state. Maybe clean/group it up a bit, but that's pretty low priority.
• The main things I want to get rid of in the app state is all the GUI element state stuff. Stuff like "scroll offset" or "cursor offset" - these shouldn't be stored in the app state as they are now. It causes this horrible interconnected mess that makes expanding really, really hard, and is the main reason I haven't been willing to even touch things like config.
• What this also entails, then, is a refactoring of how we do GUI. Currently, we have this questionable (I have no idea what I was writing) Painter class that... implements traits to draw specific elements. This is awful.
  • There is so much code dup. Our widgets are mostly just table/graphs, for example. But for those tables and graphs, each one requires a separate implementation, where 80% of the code is the same!
  • We currently store zero state in the elements. We should. It makes no sense to tie it inside app state.
  • We should also ideally move how these elements handle inputs. Ideally, we can have the option to delegate input handling within widgets if global shortcuts cannot handle them.

Issue

If applicable, what issue does this address?

Affects (maybe closes) #374, #234

Testing

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Furthermore, mark which platforms this change was tested on. All platforms directly affected by the change must be tested

• Windows
• macOS
• Linux

Checklist

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• Areas your change affects have been linted using rustfmt (cargo fmt)
• The change has been tested and doesn't appear to cause any unintended breakage
• Documentation has been added/updated if needed (README, help menu, etc.)
• The pull request passes the provided CI pipeline
• There are no merge conflicts

[ClementTsang]

Closing this for now until it's closer to being ready.