Given an m x n matrix, return true if the matrix is Toeplitz. A matrix is Toeplitz if every diagonal from top-left to bottom-right has the same elements.
Input: A 2D integer array matrix of size m x n.
Output: true if Toeplitz, false otherwise.
Input: [[1,2,3,4],[5,1,2,3],[9,5,1,2]]
Output: true
Explanation: Each top-left to bottom-right diagonal has all equal elements. Toeplitz.Input: [[1,2],[2,2]]
Output: false
Explanation: Diagonal starting at (0,0) has [1,2] — not all equal. Not Toeplitz.Input: [[1,1,1],[1,1,1],[1,1,1]]
Output: true
Explanation: All elements equal → all diagonals trivially equal. Toeplitz.m == matrix.lengthn == matrix[i].length1 <= m, n <= 200 <= matrix[i][j] <= 99