[MLIR] Extract division representation from equality expressions.

Extract the division representation from equality constraints.
For example:
    32*k == 16*i + j - 31                 <-- k is the localVariable
    expr = 16*i + j - 31, divisor = 32
    k = (16*i + j - 32) floordiv 32
The dividend of the division is set to [16, 1, -32] and the divisor is set
to 32.

Reviewed By: Groverkss

Differential Revision: https://reviews.llvm.org/D117959