Oxidize TwoQubitDecomposeUpToDiagonal (Qiskit#12563)

* Oxidize TwoQubitDecomposeUpToDiagonal

This commit ports the TwoQubitDecomposeUpToDiagonal class from Python to
rust. This internal private class is used internally by the quantum
shannon decomposition code, and while not performance critical was
simple to port. One difference is while the original Python
implementation was a class, it acted more like a function in practice.
So the new rust version is exposed as a function.

Co-authored-by: Luciano Bello <[email protected]>
Co-authored-by: Elena Peña Tapia <[email protected]>
Co-authored-by: Sebastian Brandhofer <[email protected]>
Co-authored-by: Jake Lishman <[email protected]>
Co-authored-by: John Lapeyre <[email protected]>
Co-authored-by: Julien Gacon <[email protected]>
Co-authored-by: Eli Arbel <[email protected]>
Co-authored-by: Raynel Sanchez <[email protected]>
Co-authored-by: Henry Zou <[email protected]>
Co-authored-by: Shelly Garion <[email protected]>
Co-authored-by: Alexander Ivrii <[email protected]>

* Build circuit from rust

Since Qiskit#12459 recently merged we now have a mechanism to build a circuit
from rust. This commit updates the synthesis function to build the
circuit directly in rust instead of returning a circuit sequence and
building the circuit from Python. This should speed up the construction
substantially.

* Remove unused private Python class

This commit removes the Python implementation of the function. This is
now unused in Qiskit and was never a public class so nothing external
should be depending on it. Since it's not used we should just remove it.

* Remove unused import

* Calculate best_nbasis in unwrap_or_else()

---------

Co-authored-by: Luciano Bello <[email protected]>
Co-authored-by: Elena Peña Tapia <[email protected]>
Co-authored-by: Sebastian Brandhofer <[email protected]>
Co-authored-by: Jake Lishman <[email protected]>
Co-authored-by: John Lapeyre <[email protected]>
Co-authored-by: Julien Gacon <[email protected]>
Co-authored-by: Eli Arbel <[email protected]>
Co-authored-by: Raynel Sanchez <[email protected]>
Co-authored-by: Henry Zou <[email protected]>
Co-authored-by: Shelly Garion <[email protected]>
Co-authored-by: Alexander Ivrii <[email protected]>