feat: add cluster visualization for WhileOp, IfOp, ForOp

[andrijapau]

This PR adds basic cluster visualization for these control flow operators.

⚠️ The cluster labels are not descriptive at the moment but a future PR should improve upon them (not required for MVP).

@qml.qjit(autograph=True, target="mlir")
@qml.qnode(dev)
def my_workflow(x):
    if x == 2:
        qml.X(0)
    elif x == 3:
        qml.Y(0)
    else:
        qml.Z(0)

    for i in range(3):
        qml.H(0)

    counter = 0 
    while counter < 5:
        qml.RX(0.5, 0)

[sc-103462]
[sc-103464]
[sc-103465]

[mudit2812]

2 blocking comments:

• if-elif-else blocks seems to be incorrectly handled
• WhileOp should probably have a main cluster with 2 clusters inside it, similar to an IfOp, for the before/after_regions

[mehrdad2m]

Thanks @andrijapau, looks good. I only have some concerns regarding the flattening logic.

[mehrdad2m]

I will approve to not block the PR, I think I looks good as long as the unresolved conversation is fixed.

[andrijapau]

I will approve to not block the PR, I think I looks good as long as the unresolved conversation is fixed.

Thanks, I think the fix is already in place. I posted in slack here to see product's opinion.