Surface code

[royess]

The PR adds surface codes, which are tailored toric codes that require less boundary connectivity,

• Implement surface codes based on existing toric code implementation.
• Implement a specially tailored 9-qubit surface code.
• Improve the docstrings for the toric code and add its reference paper.

[royess]

I have fixed an overwrite bug; now, most CI tasks are passed. I noticed some failures, but they seem to be unrelated to this PR.

@Krastanov, could you help review this PR? Thanks!

[Krastanov]

Thanks! This looks great!

[Krastanov]

• Let's stick to the name "Surface".
• If the 9-qubit example you have is simply an instance of the rotated surface code, let's delete it -- no need to have a single instance of a family without having the family.

[royess]

Thanks for your suggestions! The new commit removed the 9-qubit (rotated) Surface code and did the aforementioned formatting.

[Krastanov]

This looks awesome! I made some minor style suggestions and a request to plug the code example docs into the test runner, but otherwise this is good to merge.