CascadiaSettings is now a WinRT object in the TerminalApp project.
## References
#7141 - CascadiaSettings is a settings object
#885 - this new settings object will be moved to a new TerminalSettingsModel project
This one _looks_ big, but most of it is really just propagating the
changes to the tests. In fact, you can probably save yourself some time
because the tests were about an hour of Find&Replace.
`CascadiaSettings::GetCurrentAppSettings()` was only being used in
Pane.cpp. So I ripped out the 3 lines of code and stuffed them in there.
Follow-up work:
- There's a few places in AppLogic where I `get_self` to be able to get
the warnings out. This will go away in the next PR (wrapping up #885)
## Validation Steps Performed
- [x] Tests passed
- [X] Deployment succeeded
Closes#7141
c5cf7b817a