Currently, InstrRefLDV only handles DBG_VALUE instructions, not DBG_VALUE_LIST, and as a result of this it primaryil

Currently, InstrRefLDV only handles DBG_VALUE instructions, not DBG_VALUE_LIST, and as a result of this it handles these instructions using functions that only work for that type of debug value, i.e. using `getOperand(0)` to get the debug operand. This patch changes this to use the generic debug value functions, such as `getDebugOperand` and `isDebugOffsetImm`, as well as adding an `IsVariadic` field to the DbgValueProperties class and a few other minor changes to acknowledge DBG_VALUE_LISTs. Note that this patch does not add support for DBG_VALUE_LIST here, but is a precursor to other patches that do add that support.

Currently, InstrRefLDV only handles DBG_VALUE instructions, not DBG_VALUE_LIST, and as a result of this it primaryilhandles these instructions using functions that only work for that type of debug value, i.e. using `getOperand(0)` to get the debug operand. This patch changes this to use the generic debug value functions, such as `getDebugOperand` and `isDebugOffsetImm`, as well as adding an `IsVariadic` field to the DbgValueProperties class and a few other minor changes to acknowledge DBG_VALUE_LISTs. Note that this patch does not add support for DBG_VALUE_LIST here, but is a precursor to other patches that do add that support.