[msan][NFCI] Add llvm.[us]cmp (starship operator) tests (#125790)

llvm.[us]cmp is correctly handled heuristically when each parameter is
the same as the return type e.g.,
  call i8 @llvm.ucmp.i8.i8(i8 %x, i8 %y)
but handled incorrectly by visitInstruction when the return type is
different e.g.,
  call i8 @llvm.ucmp.i8.i62(i62 %x, i62 %y)
  call <4 x i8> @llvm.ucmp.v4i8.v4i32(<4 x i32> %x, <4 x i32> %y)

Forked from llvm/test/CodeGen/X86/[us]cmp.ll

Author: thurstond