Restructure and Add Tutorial to Online PyROS Documentation

[shermanjasonaf]

Summary/Motivation:

This PR restructures the PyROS online documentation and adds a new tutorial to the documentation.

Changes proposed in this PR:

• Reorganize the PyROS online documentation and split it into multiple webpages
• Add a new, extensive tutorial to the PyROS online documentation
• Replace the original quickstart example problem with a problem that is smaller, easier to write down, and less sensitive to the subsolver(s) used (see this comment of #3649)
• Add the mathematical definition of each pre-implemented PyROS UncertaintySet class to the class's docstring

TODO (after #3732 merged)

• Account for changes to the logging system in the restructured online docs
• Remove original PyROS doc ReST file; rename new PyROS doc folder as "pyros" (to preserve original PyROS docs URL)
• Update version number, changelog

Legal Acknowledgement

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1. I agree my contributions are submitted under the BSD license.
2. I represent I am authorized to make the contributions and grant the license. If my employer has rights to intellectual property that includes these contributions, I represent that I have received permission to make contributions and grant the required license on behalf of that employer.

[shermanjasonaf]

@jas-yao @natalieisenberg @jsiirola