Expand set of environments on which CI checks are run to detect OS- and OS-version-specific problems

[lbianchi-lbl]

Description

• Recently there have been some instances of solver errors that only occur on a specific OS or OS version. One example is e.g. Change value of temperature fixing by 0.001 to get around solver error in air_separation_case_study.ipynb on CentOS 8 examples-pse#83, where the solver fails when running the notebook on CentOS 8, but not on Ubuntu 18.04, which is the OS version we're using in GitHub Actions (GHA) to run our CI checks on Linux
• This is a "false negative" for our current CI setup: this error would have been caught if CentOS 8 was among the list of OSes where the CI checks are run in GHA

Possible solutions

• Configure the GHA workflows to include OSes and version that are supported by IDAES (using e.g. idaes-ext builds as a reference) but are not currently being used

Challenges

• If the OS is not one of those provided by default by GHA (as it is for e.g. CentOS), the CI job cannot be parametrized using the matrix syntax, but requires a separate job definition
• Because the number of CI jobs that can run simultaneously at a given time is limited, we should think carefully how to distribute the various OS/version combinations in the various CI workflows so that they don't "clog" the CI pipelines for the repo

[lbianchi-lbl]

Other issues that are connected with this:

• Test failure on CentOS 8 solid/gas contactor #752
• IDAES-EXT Testing #224

[ksbeattie]

Closing this as "complete" in that we don't build on CentOS anymore.