Open taskbar pinning popup view from anywhere

This CL handles both long-press and right-click events anywhere on
pinned taskbar and opens `TaskbarDividerPopupView` correctly
positioning it above the event coordinates.

Bug: 297325541
Flag: com.android.launcher3.show_taskbar_pinning_popup_from_anywhere
Test: manual for now, flip the flag, long-click or right-click
      on empty space on the pinned taskbar
Change-Id: I1849db14f65bf9478ed9f4fd39f95d08987baf8d