split a sub sub circuit

[cattabiani]

Context

This is a reference to be split in multiple sub-issues. DO NOT MERGE

fix: https://github.com/openbraininstitute/prod-build-circuit/issues/14

Test

Since it is easy to lose track of the explanations in the issue I focused on the circuit in tests/unit/data/sonata/split_subcircuit and on these extractions:

    subset_B_A = {
        "subset_B_A": ["subset_B_A_popA", "subset_B_A_popB", "subset_B_A_popC"],
        "subset_B_A_popA": {"population": "A", "node_id": [0, 2, 4, 5]},
        "subset_B_A_popB": {"population": "B", "node_id": [0, 2, 4, 5]},
        "subset_B_A_popC": {"population": "C", "node_id": [0, 2, 4, 5]},
    }
    # subset_C_A picks A:{0,2}, B:{0,2}, C:{0,2} from A
    subset_C_A = {
        "subset_C_A": ["subset_C_A_popA", "subset_C_A_popB", "subset_C_A_popC"],
        "subset_C_A_popA": {"population": "A", "node_id": [2, 5]},
        "subset_C_A_popB": {"population": "B", "node_id": [0, 2, 4, 5]},
        "subset_C_A_popC": {"population": "C", "node_id": [0, 2, 4, 5]},
    }
    # subset_C_B_A picks A:{0,1}, B:{0,1}, C:{0,1} from B_A (renumbered IDs of original {0,2})
    subset_C_B_A = {
        "subset_C_B_A": ["subset_C_B_A_popA", "subset_C_B_A_popB", "subset_C_B_A_popC"],
        "subset_C_B_A_popA": {"population": "A", "node_id": [1, 3]},
        "subset_C_B_A_popB": {"population": "B", "node_id": [0, 1, 2, 3]},
        "subset_C_B_A_popC": {"population": "C", "node_id": [0, 1, 2, 3]},
    }

With the convention: B_A means subcircuit B extracted from A. I also created a nice viz tool to understanding at first glance what is going on. Here is the initial state of the art:

Objective: the last 2 graphs should be the same (apart numbering)