[WIP] Dynamical decoupling

[eggerdj]

Summary

This PR adds support for dynamical decoupling.

Details and comments

TODO

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[ElePT]

I know this is a WIP and the notebook is unfinished, but I added a few minor comments on the content already there in case they help.

[Durd3nT]

The PadDynamicalDecoupling pass takes away the layout of the circuit. This should be highlighted in the documentation of that class, but also in tutorials such as this one.
One potential issue caused by this is that transpiling observables based on the circuit layout will fail if your workflow looks like below.

t_circ = transpile(circ, ...)
t_circ = dd_passmanager(...).run(t_circ)

t_observable = SparsePauliOp(...).apply_layout(t_circ.layout)