Update benchmark results for epochs

[psalz]

This updates the benchmark results for epochs, as we forgot to include that in #86.

Also I've switched to gpuc2 for benchmarking (using SLURM), where we can already see a reduction in noise for some benchmarks. In general the results are as expected I'd say, with epochs adding some additional cost to all graph generation benchmarks.

Intrusive graph

Generating large command graphs

Building CDAGS in scheduler thread (1 node)

Building CDAGS in scheduler thread (4 nodes)

[PeterTh]

LGTM.
One note: it would be nice to make the charts have a solid white background, currently they are unreadable on dark mode github.