Updates BannerMessagePreference to new style

Updates the style of the BannerMessagePreference in v31 and adds support
for the following new functionality (all optional):
- Use one of three attention level themes: high, medium, and low
(default: high)
- Add an icon (default: alert icon)
- Subtitle (default: hidden)
- Dismiss button (default: hidden)

Icon, subtitle, and theme can also be set via xml attrs.

Adds support for creating a BannerMessage without a title.

Test: make -j80 RunSettingsLibRoboTests
Test: Manually tested all configurations
Bug: 181764215

Change-Id: I73bfc5225d83057e423b6a9d77a6277a656d3b90