[AArch64InstrInfo] Ignore debug insts in canInstrSubstituteCmpInstr [6/14]

Summary:
Fix an issue where the presence of debug info could disable a peephole
optimization in optimizeCompareInstr due to canInstrSubstituteCmpInstr
returning the wrong result.

Depends on D78137.

Reviewers: t.p.northover, eastig, paquette

Subscribers: kristof.beyls, hiraditya, danielkiss, aprantl, llvm-commits, dsanders

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D78151