[llvm][MIRVRegNamerUtils] Adding hashing on CImm / FPImm MachineOperands.

This patch makes it so that cases where multiple instructions that
differ only in their ConstantInt or ConstantFP MachineOperand values no
longer collide. For instance:

%0:_(s1) = G_CONSTANT i1 true
%1:_(s1) = G_CONSTANT i1 false
%2:_(s32) = G_FCONSTANT float 1.0
%3:_(s32) = G_FCONSTANT float 0.0

Prior to this patch the first two instructions would collide together.
Also, the last two G_FCONSTANT instructions would also collide. Now they
will no longer collide.

Differential Revision: https://reviews.llvm.org/D71558