Multi-file comparison ability

[andrewazores]

It would be a very useful feature for the datasource to be able to load more than one source JFR file at a time, and plot the timeseries data from each on the same plots, but with some way to distinguish which file the datapoint came from. This could be simply a prefix on the timeseries key/name, ex. JVM1.cpuLoad. There could be some dashboard panel with a simple visualization like a table which maps JVM1 to the filename that provided the data. These filenames would be the ones pushed into the datasource by Cryostat, so the Cryostat server would be responsible for naming the files in a way that encodes enough identifiable information about the recording file and the target JVM it came from.