[llvm] [GlobalIsel] Visit ICmp (PR #105991)

[Thorsten Schütt via llvm-commits]

tschuett wrote:

The following two G_ICMP combines both rely on known bits:  icmp_to_true_false_known_bits and  icmp_to_lhs_known_bits. Maybe merging them could save some time. We have to compute them less often.

commute_int_constant_to_rhs and constant_fold_binop compute constants of the parameters. Merging them into one could save some time. The same is done in this PR for icmps.

https://github.com/llvm/llvm-project/pull/105991