- Introduce a method that adds a chain of `PackedInstruction` continuously avoiding the re-linking of each bit's output-node until the very end of the iterator.
   - TODO: Add handling of vars
- Add header for a `from_iter` function that will create a `DAGCircuit` based on a chain of `PackedInstruction`.

- Fix incorrect re-insertion of last_node.

- Remove `from_iter`

- Use `entry` api to either modify or insert a value if missing.

- A bug that adds duplicate edges to vars has been temporarily fixed. However, the root of this problem hasn't been found yet. A proper fix is pending. For now skip those instances.

- A set collecting all the new nodes to connect with a new node was preventing additional wires to connect to subsequent nodes.

… nomenclature.

- Caught by @ElePT

Co-authored-by: Elena Peña Tapia <57907331+ElePT@users.noreply.github.com>

- Use Entry API to modify last nodes in the var.
- Build new_nodes with an allocated vec.
- Add comment explaining the removal of the edge between the output node and its predecessor.

- Use `or_insert_with` instead of `or_insert` to perform actions before inserting a value.