Module detection currently requires calling the registry to determine
the subdirectory. Since we're not directly accessing the subdirectory
through FolderStorage, and now handling it within terraform so modules can
reference sibling paths, we need to call out to the registry every
time we load a configuration to verify the subdirectory for the module,
which is returned during the Detect.
Record the subdirectories for each module in the top-level of the
FolderStorage path for retrieval during Tree.Load. This lets us bypass
Detection altogether, modules can be loaded without redetecting.
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