[refactor, fix] Dataflow Analysis Interface and Lattice Interface

[yhteoh]

• Please check if the PR fulfills these requirements

• The commit message follows our guidelines
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)
  fix

• What is the current behavior? (You can also link to an open issue here)

• Uses LatticeBottom as default value of unassigned key
• CFG after CFGBlockAccumulator blocks ids are not consecutive
• No control over initial state
• No max number of iterations in DataflowAnalysis
• DataflowAnalysis.analyze takes in merge_function, even though merge_function is determined by the analysis
• CFGBlock.edge_labels in form node id to label
• BackwardDataflowAnalysis flips in_states and out_states when returning
• maplattice incorrect type hints

• What is the new behavior (if this is a feature change)?

• lattice changes

  • maplattice able to determine behavior for undefined keys, one of [flexible, top, bottom, strict]
  • Refactor maplattice by enabling caching and implementing a base class MapLattice for dynamically generated subclasses to inherit from
  • Added LatticeMeta to manage singleton instances of Lattice

• dataflow changes

  • Added max iterations for DataflowAnalysis
  • Added abtractmethod for DataflowAnalysis for default initial state based on graph
  • Added argument to DataflowAnalysis.analyze to use an initial state
  • Added argument to determine max number of iterations for DataflowAnalysis
  • Added abstractmethod DataflowAnalysis.merge to specify merge function to use instead of as an argument to DataflowAnalysis.analyze
  • Fixed BackwardDataflowAnalysis flips to return the in_states and out_states correctly`
  • DataflowResult now contains the DataflowAnalysis used to generate it

• cfg changes

  • use sets for CFGBlock.succs and CFGBlock.preds
  • Reversed CFGBlock.edge_labels to be of form label to node id
  • Add tags for CFGBlock
  • Added RelabelCFGBlocks to relabel block ids such that they are consecutive

• Does this PR introduce a breaking change? (What changes might users need to make in their application due to this PR?)
  major

• take note of new default behavior of maplattice operations
• major change to DataflowAnalysis interface

• Other information: