Add graphviz-esque based visualization for callgraphs

Table-flip the work I did in the past few commits and use dagre-d3 to
make a nice graphviz-esque visualization for the callgraph. This new UI
is missing a useful UI elements that will need polish. For example:

* Details on the current node are missing.
* It would be ideal to have symbol details (all metrics, child
  functions) for the currently focused node.
Start making chart a bit easier to read.

* Add colors & size variance based on weight of function.