Add MPS and GZ support in `translators`

[dthuerck]

✅ I have added the tests to cover my changes. ✅ I have updated the documentation accordingly. ✅ I have read the CONTRIBUTING document.

Summary

See issue #582: This PR succeeds #581, having moved lp/mps/gz IO functions into translators.

Details and comments

lp functions in QuadraticProgram have been marked as deprecated. Tests and Tutorials have been updated to use the file_io.

[coveralls]

Pull Request Test Coverage Report for Build 8389542132

Details

• 93 of 95 (97.89%) changed or added relevant lines in 4 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.06%) to 93.089%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
qiskit_optimization/translators/file_io.py	77	79	97.47%
<!--	Total:	93	95	97.89%	-->

Totals
Change from base Build 8048858331:	0.06%
Covered Lines:	4580
Relevant Lines:	4920

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💛 - Coveralls

[dthuerck]

@woodsp-ibm Thanks for the hints! Should be all done by now, release note is there.

[dthuerck]

Thanks for the extensive comments, @woodsp-ibm ! I added test cases for the deprecated functions and updated the docs accordingly.