This commit introduces a basic ApplicationState class, without being used for anything yet to aid reviewers. At a later point actual usages of this new class may be added separately.
## References
This commit is an initial step towards implementing #8324.
## PR Checklist
* [x] I work here
* [x] Tests added/passed
## Validation Steps Performed
* Creating a `state.json` with `{"generatedProfiles":["{53e75ed9-2b63-4118-856d-0510c4f6b97e}"]}` updates the ApplicationState, as observed through a debugger ✔️
* Deleting the "generatedProfiles" field sets the corresponding field back to nullopt ✔️
This guide serves as a reference on how to add a setting to Windows Terminal. It covers...
- Terminal Settings Model changes
- Settings UI changes
- `TerminalSettings` changes
- Actions and action arguments
As a part of #6800 (Settings UI Follow Up Tasks)
