Add a transform get_unitary_matrix to obtain matrix representations of circuits

[ingstra]

Context:

Create a new function to construct the unitary matrix corresponding to any quantum circuit.

Description of the Change:

The new transform get_unitary_matrix works similarly to _apply_unitary() in devices/default_qubit.py.
Benefits:

Can process all operations, including controlled gates on non-adjacent wires or wires in reverse order.

Possible Drawbacks:

Related GitHub Issues:
#1462

[rmoyard]

Hi @ingstra, thanks for the update. You can follow Josh's advice on how to reduce the number of ifand else, this should solve the last problem 💯

[ingstra]

Why is Sphinx suddenly failing? The error message is not very forthcoming:

[sphinx-action] Build failed with 0 warnings
Traceback (most recent call last):
File "/entrypoint.py", line 22, in
action.build_all_docs(github_env, [os.environ.get("INPUT_DOCS-FOLDER")])
File "/sphinx_action/action.py", line 167, in build_all_docs
raise RuntimeError("Build failed")
RuntimeError: Build failed

[rmoyard]

Hi @ingstra, it looks good on my side thank you again for the great work! 💯 I let @glassnotes give a final review.

[glassnotes]

@ingstra this is awesome!! 💯 All but one of my suggestions here is just formatting. The only thing left to add is an interface test for JAX, which will look quite similar to the other interface tests. Once that's in, it's ready to merge 🚀

[ingstra]

Thanks @glassnotes! I accepted your suggestions and added a test with JAX.

[glassnotes]

@ingstra changes looks great, this is ready to go! 🎉 It looks like there will be a few merge conflicts when updating the branch, let me know if you run into any trouble with those.