## Summary of the Pull Request
Adds the `setColorScheme` action, to change the color scheme of the active control to one given by the `name` parameter. `name` is required. If `name` is not the name of a color scheme, the action does nothing.
## References
* Being done as a stepping stone to #6689
## PR Checklist
* [x] Closes#5401
* [x] I work here
* [ ] Tests added/passed
* [n/a] Requires documentation to be updated
## Detailed Description of the Pull Request / Additional comments
Technically, the action is being done by changing the settings of the current `TerminalSettings` of the `TermControl`. Frankly, it should be operating on a copy of the `TermControl`'s `IControlSettings`, then updating the control's settings, or the Control should just listen for changes to it's setting's properties, and update in real time (without a manual call to `UpdateSettings`. However, both those paths are somewhere unknowable beyond #6904, so we'll just do this for now.
## Validation Steps Performed
* tested manually with a scheme that exists
* tested manually with a scheme that doesn't exist