IDEA-CR-26759

This simplifies writing build scripts (previously it wasn't evident which modules should be included into platformApiJarModules, and which into productApiModules, javadoc for the both fields referred to CommunityRepositoryModules#PLATFORM_API_MODULES). Also this unifies layout of different products, all of them will have the same platform-api and platform-impl JARs after migration to the new productApiModules/productImplementationModules properties.

Asked by Andrey Cheptsov

Review ID: IDEA-CR-27166

The change is needed to avoid overlaps with real index versions that
have version advancements from 0 to 1

to hopefully reduce the number of test failures due to not fully gc-ed references

compose tests into one