mgr/dashboard: Replace OSD histogram graphs with something more insightful
Currently, the OSD details contain a tab "Histogram" that shows a feature that was ported from the initial dashboard without any modification.
It displays two big red blocks labeled "Writes" and "Reads" as follows:
It's not entirely clear what kind of information these blocks are supposed to visualize and if they are actual "Histograms".
It may make sense to reconsider the design of these widgets with something more useful. Maybe a heat map, combining reads and writes into once graph?