Allow A11yService to customize accessibility focus

1. Define and implement new APIs to set and get the stroke width
and color of the A11y focus rectangle.
2. New an AccessibilityFocusApperanceData variable with the default
value in the A11yUserState class, and it would be used in the A11y
framework.
3. When A11y services sets the stroke width and color of the focus
rectangle, A11yUserState will apply the same value through
A11yServiceConnection and notify this change to A11yManager.
4. When A11y services customized the data is disabled, reseting the
data in the A11yUserState and notifying this change to A11yManager.
5. When the ViewRootImpl gets the A11yFocusDrawable, it changes the
strokewidth and the color of this drawable based on the value from
A11yManager.

Bug: 141144573
Test: a11y CTS & unit tests

Change-Id: I1493f17f7cc25744e1435c9070218c6f7efa8bcf