Instantiate a new ScreenshotController if consecutive request are for different displays

Just dispose of the old controller if it's for a different display.
Eventually we could make them coexist, but that carries more risk.

Bug: 412987428
Test: atest TakeScreenshotExecutorTest
Test: manual testing with a connected display
Flag: com.android.systemui.screenshot_multidisplay_focus_change
Change-Id: Ie33d12ea19ad89ab93294aac195a166f329bea4d