FR Understand proguard-only projects

Some projects contain only proguard files used by AGP. Example: https://github.com/artem-zinnatullin/RxJavaProGuardRules

Might be tricky as other "unused" projects would still have their proguard files being used. I think a reasonable middle ground is to only ignore them if they _only_ have proguard files included and nothing else.

Alternatively could be handled by an exclusion extension of some sort

Start by tracing how the Gradle plugin identifies unused projects and how it sees Android ProGuard files, then compare the behavior with the linked RxJavaProGuardRules example. Done means projects containing only ProGuard files used by AGP are ignored, while projects with other content are still analyzed; no repository file or test is named in the issue.

Written by the indexing model from the issue text.