This PR extends the `Label` component with additional functionality,
partially for use in the `TextTooltip` component.

- [x] `Label` should take a `size` (`Default` & `Small` for now)
  - These should use `text_ui` and `text_ui_sm`
- [x] Fold `LabelColor` and `IconColor` into one enum
  - `TextColor`
- [x] `TextTooltip`'s keybinding field should take whatever we use for
keybindings instead of a string, and render the keybinding component
- [x] `TextTooltip` should use small `Label`s

Release Notes:

- N/A