FasterFilesystemForeignSourceRepository is not working as expected

The optional ForeignSourceRepository implementation called FasterFilesystemForeignSourceRepository, designed to keep all the requisitions on a cache and update the cache when the imports or foreign-source directories are changed, is not working as expected.

The JUnit tests designed for FasterFilesystemForeignSourceRepository and DirectoryWatcher are not covering all the use cases, which is why the problem was not caught before.