Fix bug with long strings not aligning left on menu items

This CL sets gravity="start" and ellipsize="end" so that longer strings in the Overview app dropdown menu are still left-aligned and ellipsized when they are longer than the container.

Fixes: 330426535
Flag: N/A
Test: Manual
Change-Id: I1e62412c9b8be41a8dbb6b0597a69a283a56e3f0