Highlight the executing node with stack_data

[alexmojaki]

Here's what it's all been about! Closes #11827

Example script:

def foo(i):
    x = [[[0]]]
    return x[0][i][0]


def bar():
    return foo(0) + foo(
        1
    ) + foo(2)


bar()

Output:

[Carreau]

Whooo !

[alexmojaki]

Hooray!

Can you sort out choosing proper colors based on configuration?

[Carreau]

Opened #12151 to track that.