[feature] Call graph: Subgraph hiding (HoleNode)

[Domiii]

• Add a configurable filter predicate that determine what kind of context gets hidden (aka filtered).
• Add new HoleNode that serves as a group for "hidden" nodes. All filtered contexts that are directly connected (i.e. all siblings and parents/children, recursively) get grouped into one such node.
  • → see new CallGraphNodes.floodHole algorithm
• fix getComponents('ContextNode')
• fix floodHole algo: non-root holes contain root contexts
• fix: allow extending of existing root holes (rather than creating new ones that also contain the old ones)
• Make the new HoleNode a bit prettier
• Add button to toolbar to allow customizing the context filters
  • V3: add one button per filter option in a dropdown
    • each button renders as "activated" if it does not equal its default
      • default is empty, except for packageWhitelist which is .*)
    • when clicked: 1. show quickpick of history (sorted by lastUsed), 2. plus one entry in the beginning which is <add new>
    • when (1) is selected, move it (don't duplicate it) in the history array
    • when (2) is selected, show InputBox to allow user producing a new filter

• Store filter history in memento
  • Expose memento get/set in graph externals
• test w/ react-tic-tac-toe → it has almost only library nodes

ACG subgraph hiding

• Also add subgraph hiding to ACG
• re-purpose the floodHole algorithm, but traverse AsyncEdges instead of in-root contexts (can we generalize the original, without degrading performance?)
• When adding a node to a HoleNode, we need to re-determine FORK or CHAIN:
  • 
  • In the above example, we want to add 3 green nodes to the blue HoleNode (spanning the blue subgraph).
  • → 1 is CHAINed while 2 and 3 are FORKed from the HoleNode

[Domiii]

First results (graph-filter-test1.js):