Investigate streamlining and automating testing

[tbirdso]

Overview

One major weakness of developing reusable Github Actions (GHA) build workflows such as those in ITKRemoteModuleBuildTestPackageAction is that it is difficult to test the automated tools in an automated fashion. It would be useful to be able to test proposed changes against some minimal project to ensure that build/test/package functionality is as expected.

Proposed Investigative Paths

1. Embed workflows-under-test within another workflow in ITKRemoteModuleBuildTestPackageAction/.github/workflows. The outer workflow could checkout a small demo project from another module and use the inner workflow to build/test/package said project. Unclear at the moment whether the reusable workflow can be embedded in this way.
2. Direct users to manually run the test external module against their PR. This method is known to work due to testing with ITKSplitComponents, but requires extra effort and is therefore less approachable and less sustainable.

Additional Notes

See original discussion by @jhlegarreta in #45 (comment)