Given a matrix grid of size $m \ * \ n$, where each row and column is sorted in non-increasing order, find and return the total count of negative numbers in the matrix.

Constraints:

• $m$ $==$ grid.length

• $n$ $==$ grid[i].length

• $1\leq$ $m$, $n$ $\leq 1000$

• $-100 \leq$ grid[i][j] $\leq 100$