Add passes to convert arith.remui to use the arith_ext ops

[inbelic]

Cf #635.

Add the following passes to arith_ext:

• Create a pass that converts arith.muli + arith.remui into arith.muli + artih_ext.barret_reduce + arith_ext.subifge when the operands are in the range [0, cmod).
• Create a pass that converts arith.addi + arith.remui into arith.addi + arith_ext.subifge when the operands are in the range [0, cmod).
• Create a pass that converts arith.subi + arith.remui into arith.subi + arith.addi cmod + arith.subifge when the operands are in the range [0, cmod).