Add Zoom Controls widgets

### Problem

Zoom buttons and scales are used in a fair amount of apps. The buttons (or the idea styled the same) are used in at least Web, Code, Files, and -- in the community -- Jorts. The scale is less used, but it is still present in Photos, and probably some other community apps. Therefore, I think it's reasonable to provide a widget built into the library, so that all uses will have common accelerators, styling, etc., and we don't have to repeat ourselves so many times across apps.

### Proposal

Add two widgets:

- Zoom buttons
- Zoom scale

### Prior Art (Optional)