IGV: dump and visualize node bottom and phase types

Dump node bottom types (i.e. Node::bottom_type()) and types used during GVN, IGVN, and CCP (i.e. PhaseValues::type(Node* n)) when available. This makes it possible to capture and track the type state of each node with greater detail than what is possible now. Attached is a screenshot of a prototype 'Show type info' filter (right graph) displaying the phase type of each node as part of its label.