Moves the existing points-to predicates to the newly added class
`ControlFlowNodeWithPointsTo` which resides in the `LegacyPointsTo`
module.
(Existing code that uses these predicates should import this module, and
references to `ControlFlowNode` should be changed to
`ControlFlowNodeWithPointsTo`.)
Also updates all existing points-to based code to do just this.
With this change, users are now able to run View AST command in
vscode within vscode workspaces that do not include the core libraries.
The relevant core library only needs to be installed in the package
cache.
