PyomoNLP scaling factors on sub-blocks

[bknueven]

Fixes # N/A

Summary/Motivation:

Scaling factors in the PyomoNLP interface will not be applied if the scaling_factor Suffix is on a sub-block.

Changes proposed in this PR:

• Change PyomoNLP scaling determination methods to use SuffixFinder instead (23d316e, a7791e1)
• Change PyomoGreyBoxNLP and PyomoNLPWithGreyBoxes to use SuffixFinder (8215ef8, c7b1bca)
• Maintain backwards compatibility (9ca3928)
• Update the tests so they fail with nested scaling_factors (0b4d16b)

As-is this PR would change the behavior of these methods in that they would always return scaling factors. I cannot seem to exactly replicate the prior behavior which would allow all existing tests to pass without modification.

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[bknueven]

Thanks for the PR, this is a good change. I have a minor concern about backward incompatibility, see below. Also, can you add a small unit test to TestPyomoNLP in test_nlp.py that exercises this functionality?

Thanks for the review. I believe I have address all comments except for potential modifications to SuffixFinder to support a context argument. I believe the same potential issue would also affect the NL writer.