BandwidthTestHandler: Handle duplicated comparisons e.g. a LumiLine in all streams

lhcb/Moore!2994 (comment 7817681) showed up a corner case in the comparison pages for the bandwidth tests made by BandwidthTestHandler: if we have a line duplicated in multiple streams, e.g. the LumiLine, the comparison page may fail. I managed to find a solution such that if there are lines in multiple streams with the same number, we'll get a comparison page that still builds, at the cost of all the line names getting an integer appended to them.