[DevTask] Refactor state into AppState

[robinjhuang]

Brought up in retro. This will make the desktop app easier to write code for and test.

Curious how state is handled in:

• https://github.com/vercel/hyper
• https://github.com/desktop/desktop

┆Issue is synchronized with this Notion page by Unito

[christian-byrne]

• Hyper: Redux store https://redux.js.org/api/store
• GH Desktop: Various stores for different types of data https://github.com/desktop/desktop/tree/3f224080dd0a9cea5a981bdd977509cf4a775630/app/src/lib/stores. A lot of the stored data uses remote database.

I will use electron store for now because we already are using it. Once all components of the app are using the same store and accessing with same methods, changing library or implementation will be relatively easy.