[Refactor] Use QuantumCircuit for Expr and user data + embeddings

[Doomsk]

QuantumCircuit can have as input either an expression (Expr) or user data + embedding function. User data can be any kind of array, graph, etc that contains or encodes relevant data for building a layout for the registers. It could be described as in:

class QuantumCircuit:
    @singledispatchmethod
    def __init__(self, data, **kwargs):
        raise NotImplementedError

    @__init__.register
    def _(self, data: Expr, **_: Any):
        self.circuit = data

    @__init__.register
    def _(self, data: np.ndarray, embedding: Callable):
        self.circuit = embedding(data)

    @__init__.register
    def _(self, data: list, embedding: Callable):
        self.circuit = embedding(data)

    @__init__.register
    def _(self, data: nx.Graph, embedding: Callable):
        self.circuit = embedding(data)