## Summary of the Pull Request
This PR adds a global "language" setting, which may be set to any supported BCP 47 tag.
Additionally a ComboBox is added to the settings UI under "Appearance", listing all languages with their localized names.
This PR introduces one new issue: If you change the language while the app is running, the UI will be in a torn state, as not all UI elements refresh automatically if the `PrimaryLanguageOverride` is changed.
## PR Checklist
* [x] Closes#5497
* [x] I work here
* [x] Tests added/passed
* [ ] Documentation updated. If checked, please file a pull request on [our docs repo](https://github.com/MicrosoftDocs/terminal) and link it here: #xxx
* [x] Schema updated
## Validation Steps Performed
* UI language changes when changing the "language" in settings.json before starting WT / while WT is running. ✔️
* "language" field is removed from settings.json if "Use system default" is selected. ✔️
* "language" field is added or updated in settings.json if any other language is selected. ✔️
* Removes qps- languages if debugFeatures is false. ✔️
* Correctly refreshes all UI elements with the new language. ❌
This commit introduces the terminal settings editor (to wit: the
Settings UI) as a standalone project. This project, and this commit, is
the result of two and a half months of work.
TSE started as a hackathon project in the Microsoft 2020 Hackathon, and
from there it's grown to be a bona-fide graphical settings editor.
There is a lot of xaml data binding in here, a number of views and a
number of view models, and a bunch of paradigms that we've been
reviewing and testing out and designing and refining.
Specified in #6720, #8269
Follow-up work in #6800Closes#1564Closes#8048 (PR)
Co-authored-by: Carlos Zamora <carlos.zamora@microsoft.com>
Co-authored-by: Kayla Cinnamon <cinnamon@microsoft.com>
Co-authored-by: Alberto Medina Gutierrez <almedina@microsoft.com>
Co-authored-by: John Grandle <jograndl@microsoft.com>
Co-authored-by: xerootg <xerootg@users.noreply.github.com>
Co-authored-by: Scott <sarmiger1@gmail.com>
Co-authored-by: Vineeth Thomas Alex <vineeththomasalex@gmail.com>
Co-authored-by: Leon Liang <lelian@microsoft.com>
Co-authored-by: Dustin L. Howett <duhowett@microsoft.com>
Signed-off-by: Dustin L. Howett <duhowett@microsoft.com>
