Increase menu paddings to draw shadows correctly.

Adding the menu to a System-level container could potentially crop it if
the container is exactly the size of the menu. This increases the
container's width and height by a bit so that the menu can draw its
shadow correctly.

Bug: 399926630
Test: Manual. See shadows correctly now on Handle Menu.
Flag: EXEMPT bugfix

Change-Id: I6c454db2e97dc438ddbeab9d9a3010f0c6d895a1