Resolve "Simulate SFG"

Closes #22 (closed) and #24 (closed). This merge will:

• add some important test cases
• implement deep copying of SFG
• implement Simulation
• add Register operation
• refactor operation evaluation to allow for simulation of registers/delays with loops and nested SFGs
• refactor neighbors/parameter/traverse interface by moving it to GraphComponent
• add some convenience functions to Operation
• tidy up the method signatures of some interfaces to be more general
• move bit length specification from InputPort to Signal
• add customization point for specifying input truncation behavior for user operations

b_asic/signal_flow_graph.py

@@ -156,7 +156,7 @@ class SFG(AbstractOperation):
                 if signal.source.operation not in self._original_components_to_new:
                     self._add_operation_connected_tree_copy(signal.source.operation)
     
-    def __str__(self):
+    def __str__(self) -> str:
         """Get a string representation of this SFG."""
         output_string = ""
         for component in self._components_ordered: