Create a long-press menu for sending screenshots to bubbles.

Test: Manual. Enable the long-press bubble menu with "adb shell settings set secure allow_bubble_menu 1". Then, long-press on a bubble to show a menu and tap the screenshot button to send a screenshot to the selected bubble. This won't work when the bubble is expanded.
Change-Id: I35380a8a4775e568699cf4527c6071bf932eb715