Build Accumulator to collect multiple contiguous statements into one Block in the Control flow graph

[vishnu-m77]

• 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, ...)
  Feature

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

• ControlFlowGraph stored in oqd-core
• Each statement line in the code is stored in a new Block in the ControlFlowGraph.

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

• Control Flow Graph moved to oqd-compiler-infrastructure
  • ControlFlowGraph renamed to CFG
  • Block renamed to CFGBlock
• Contiguous statements are absorbed into one block in the CFG by running the CFGBlockAccumlator pass
• Refactor cfg_to_dot visualization of control flow graph as a dot graph

• Does this PR introduce a breaking change? (What changes might users need to make in their application due to this PR?)
  Yes, Blocks do not have a kind parameter. Block.stmt is now Block.stmts as they can hold multiple statements.

• Other information:
  N/A

[yhteoh]

Looks good to me!