WIP: Local folding

[WrathfulSpatula]

Context:

Unitary Fund has partnered with Xanadu PennyLane Catalyst to add local folding functionality to Catalyst. As discussed previously, the implementation does not yet match the unit test, but we would like to share the content state of progress, for feedback.

Description of the Change:

This is a work-in-progress to add local folding functionality, of all gates in a quantum circuit, to Catalyst, with a unit test. (Local folding of random gates in a circuit will follow, after this PR.)

Benefits:

Local folding, of single quantum gates, is an alternative method to global folding, of the entire circuit effectively as a single overall operator. Certain circuits and quantum computer architectures might benefit more from either method.

Possible Drawbacks:

There are no particular drawbacks to offering an additional option of local folding, along with global folding.

Related GitHub Issues:

https://github.com/PennyLaneAI/catalyst/issues/755