Given a two-dimensional array a of integers and row/column positions r, c, return a 3x3 array whose middle element is a[r][c], and whose neighbors are copied from the original.
Given a two-dimensional array a of integers and row/column positions r, c, return a 3x3 array whose middle element is a[r][c], and whose neighbors are copied from the original. Set non-existent neighbors to zero.