Fix face education UX for both grid and traffic light

Makes the following adjustments to the UI of the Face Unlock education
screen for both the grid and traffic light enrollment flows:
- Fixes issues with text being overlapped by illustrations
- Prevents views from moving vertically due to state changes
- Ensures no scroll is required for default locale and scaling
- Adjusts the color and content of the a11y setup toggle

Test: Manual:
1. Start grid-based face enrollment (e.g. from Settings > Security)
2. Proceed to "How to set up Face Unlock" screen
3. Tap "Setup for limited vision or head motion"
4. Toggle "Setup for limited vision or head motion" switch off and on
5. Repeat steps 1-4 for traffic light face enrollment

Fixes: 191105436
Fixes: 191317385
Change-Id: Ie80f5b3130b5b0aeceb889f53cc2dec8c7423e47