Supporting multi-display for takeScreenshot()

Creating a new API, screenshotWithoutSecureLayer(), to get the
graphic buffer of screenshot for all displays including non-default
display and virtual one. We can use it to support multi-display
of takeScreenshot() API.

Bug: 145893483
Test: a11y CTS & unit tests
Test: manual testing to take screenshot of second display which is a
monitor with chrome cast

Change-Id: I474c71f7e01d57b5a318b2a5bfb690a2e01c128c