Add BUGREPORT_FLAG_CAPTURE_MULTI_DISPLAY_SCREENSHOT to BugreportParams

BUGREPORT_FLAG_CAPTURE_MULTI_DISPLAY_SCREENSHOT is to capture
screenshots of all displays.

When the flag is set, startBugreport() throws a zip file including them
via screenshotFd.
It activates only when
FLAG_BUGREPORT_MULTI_DISPLAY_SCREENSHOT_ENABLED is enabled.

Test: Build and manual test
Bug: 364767133
Flag: android.os.bugreport_multi_display_screenshot_enabled
Change-Id: Iba3059ac14a19f19ecda29047bbede0b0b400638