Build: Add tests for package installs

[WhoBrokeTheBuild]

Add "Test Packages" stage to Jenkinsfile
Add a new flag to build.py, --test-package-install, which must be run with/after --package. This will create a stock docker container and attempt to install the packages and then do a small test
Add --dockerimage-target to build.py to be used with --test-package-install
Add --dockerimage-target to most debian/redhat/windows .opts files
Standardize --platform in all updated .opts files

Refactor build.py to avoid duplicating the code in do_docker

• Add run_docker to handle most docker-related functions
• Add get_redhat_package_version/get_exe_version for converting 1.2.3 -> 1.2-3 version formats

[mwinkel-dev]

HI @WhoBrokeTheBuild -- I'm curious why the two new Ubuntu 26 *.opts files did not also need changing. Were they omitted from this PR because their changes are in a different PR?

[mwinkel-dev]

The changes to the *.opts files are straightforward.

The most complex change was the refactoring of build.py. The review used a diff of that file in the slw-test-package-install branch with that in the alpha branch. A careful comparison shows that code blocks were moved around but none were dropped. There were also some minor code cleanup changes.

Summary is that these changes match the PR's description. It is excellent that automated install tests are part of the build process.

NOTE: Eventually the two new Ubuntu 26 *.opt files should also add the "test installer" arguments. That can be done after this PR is merged.

[santorofer]

This looks good, and I have seen it being testing and working correctly.