Javadoc
Finds the area around the cells encoded in packed, without including those cells. For each "on"
position in packed, expand it to cover a a square with side length equal to 1 + expansion * 2,
centered on the original "on" position, unless the expansion would take a cell further than 0,
width - 1 (for xMove) or height - 1 (for yMove), in which case that cell is stopped at the edge.
If a cell is "on" in packed, it will always be "off" in the result.
Uses 8-way movement (Chebyshev distance) unless the overload of this function that takes a boolean argument
eightWay is used and that argument is false.
Returns a new packed short[] and does not modify packed.