change `LABEL` of unsigned-bytes to its own "absolute address" object

[stylewarning]

right now, absolute jumps are conflated in the label object here. I'd prefer we instead introduce a new object called absolute-program-location or something like that. (I don't want to use "address" only because it feels too dishonest.) If we do this, then we'd change patch-labels to not overwrite these label objects, and we'd change the QVM to know how to interpret this object.