Add ScipyMilpOptimizer

[t-imamichi]

Summary

Adds ScipyMilpOptimizer based on Scipy's MILP solver.
Scipy introduced MILP solver since 1.9.0 (supports Python 3.8 or newer).

supersedes #447

This PR is a QAMP 22 fall project by @Dran-Z qiskit-advocate/qamp-fall-22#2

Details and comments

• add more unit tests
• update reno
• update requirements.txt?

[coveralls]

Pull Request Test Coverage Report for Build 4932946655

• 78 of 78 (100.0%) changed or added relevant lines in 3 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.1%) to 92.312%

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Totals
Change from base Build 4932878321:	0.1%
Covered Lines:	4443
Relevant Lines:	4813

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💛 - Coveralls

[woodsp-ibm]

Since we run coverage along with the other checks under 3.7 and this new code is not supported in that version this would explain the coverage drop. In Nature I had already bumped the checks to run under 3.8 - since we build/deploy docs under 3.8 and we build a documentation zip as part of the checks. I had bumped it since 3.7 is nearing EOL and I wanted to ensure that what I was seeing in the docs was indeed the same as what we published. This is a simple one line change and could be done in a separate PR to check things out - then once the branch is updated here we would get a better idea of the coverage of this new code.

[t-imamichi]

Thank you for your information. I will bump Python version for the check.

[woodsp-ibm]

LGTM. 100% test coverage of the ScipyMilpOptimzer - nice!

[a-matsuo]

LGTM!