Add Python 3.12 Support

[mrmundt]

Fixes #3014

Summary/Motivation:

This updates the Pyomo build harness, and includes fixed so that tests pass on Python 3.12

Changes proposed in this PR:

• Update slice detection logic to support hashable slice objects (added in Python 3.12)
• Update Trustregion tests (tolerance and API)
• Update a magic number used for recursion testing

Legal Acknowledgement

By contributing to this software project, I have read the contribution guide and agree to the following terms and conditions for my contribution:

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.

[blnicho]

Missed reference to supported Python versions in:
https://github.com/Pyomo/pyomo/blob/main/doc/OnlineDocs/installation.rst

This is a non-functional change so I'm fine with waiting for the currently running tests to pass and then making this minor change and merging.

[mrmundt]

Missed reference to supported Python versions in: https://github.com/Pyomo/pyomo/blob/main/doc/OnlineDocs/installation.rst

This is a non-functional change so I'm fine with waiting for the currently running tests to pass and then making this minor change and merging.

I have it queued up to push when these tests complete.

[mrmundt]

Missed reference to supported Python versions in: https://github.com/Pyomo/pyomo/blob/main/doc/OnlineDocs/installation.rst
This is a non-functional change so I'm fine with waiting for the currently running tests to pass and then making this minor change and merging.

I have it queued up to push when these tests complete.

Jk, @jsiirola was impatient ;)