CallGraph analysis does not save its result on disk

[arfio]

Bug Description:

Currently a cache is maintained in the FlameGraphDataProvider, saving the result of the callgraph analysis in an in memory state system. This should be saved by the CallGraphAnalysis because this result could be saved on disk and avoid recomputing the callgraph when reopening the trace.

Steps to Reproduce:

1. Running any analysis providing a call graph
2. Closing the trace
3. Reopening and opening the flamegraph makes it compute the callgraph again.