Generated source directories by plugin name.
Can be used in SourceDirectorySet.srcDir or similar srcDir functions from other source set directories.
Marked Internal because the entries are subdirectories of outputDirectory, which is already tracked as an OutputDirectory. Declaring both would make Gradle flag overlapping outputs and refuse to cache this @CacheableTask. Consumers that pass this provider into srcDir(Provider) still get a task dependency because it is derived from the task's TaskProvider via map, independent of this annotation.