Move requirements into subpackages

[mpharrigan]

• extra-requirements.txt per subpackage
• Right now: union all the extra requirements into install_requires and add extra_requires for each subpackage (setup.py)
• Next: modify notebooks to install using e.g. recirq[qaoa]. Remove extra requires from install_requires. This stepwise change is necessary since the notebooks install from github Separate extra requirements for specific experiments #231
• Next: independent test jobs for subpackages to make sure the requirements are correct.

Annotated change:

# optimize
scikit-learn  # (moved to extra-requires)

# qaoa
networkx   # (transitive from cirq-core)
pytket-cirq~=0.16.0   # (moved to extra-requires)

# quantum chess, only needed for tests
scipy    # (transitive from cirq-core, test requirements shouldn't be here)

# hfvqe
openfermion~=1.2.0    # (moved to extra-requires)
# fix bug with openfermionpyscf https://github.com/quantumlib/ReCirq/issues/200#issuecomment-923203883
h5py~=3.2.1   # (moved to extra-requires)

# fermi_hubbard
tqdm  # notebook progress bars (transitive from cirq-core)

# otoc
Py-BOBYQA   # (moved to extra-requires)

[dstrain115]

Seems fine but for two comments.

[dstrain115]

Should this link to a Github issue?

[mpharrigan]

done, also see #231

[dstrain115]

Is there a good way to auto-detect this (or alternatively, for keeping this up to date if we add more experiments)?

[mpharrigan]

Yes, I first wrote it to glob/regex for extra-requirements.txt and I could set it to that. However: for my next thing I want to add CI jobs that tests each subpackage in isolation. Autogenerating CI jobs would likely be more complicated than its worth. Especially since there will be an isolated "vanilla deps" build that will run all tests not in the named extra-requires subpackages which would fail if newly added experiments did indeed have extra requirements.

[dstrain115]

Ok, SGTM, I already approved this PR. Feel free to merge when ready.