Problem 42501. Toeplitize a matrix

Similar to Problem 3094. Hankelize a matrix, now consider Toeplitization of a matrix.

Given an input matrix A, convert it to a Toeplitz matrix B by replacing the diagonal of A with the mean of the respective diagonal. For example,

Input

   A = [6     3     2     7

        3     5     1     2

        3     7    10     2]

Output:

   B = [7     2     2     7 

        5     7     2     2

        3     5     7     2]