Add new floating action menu for Accessibility targets. (1/n)

Goals:
- Trigger actions of accessibility features would be grouped into the floating menu.

Patch action:
1. Use current Accessibility Target functions to get the corresponding data.
2. The position of the floating menu is at the bottom-right corner of the screen initially.
3. Support dark theme.

Bug: 173958541
Test: atest AccessibilityFloatingMenuTest AccessibilityFloatingMenuViewTest
Change-Id: I28e729520d4eb8ecb0bcc41d4de9d1499380e7f5