Extend sorted_robust API

[jsiirola]

Summary/Motivation:

The idea of your PR is generlly good, however, the sort in _component_data_iter really needs to use the itemgetter(0) so that sorting doesn't accidentally compare component data objects (the second item in the tuple).

This PR updates the sorted_robust() API so that it supports the key= and reverse= arguments and puts the `itemgetter)0) back in. ...plus this adds a test of the problematic behavior from Pyomo#1845

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