The getter.Storage abstraction is proving entirely inadequate here, but
we can't replace it wholesale at the moment.
The Tree loader needs to know the location of the manifest before it can
start loading any modules. Since the version will have to be part of the
hashed storage key, there is no way to know what version of each module
are stored. The storageDir function will extract the StorageDir field
from the underlying FolderStorage instance for the tree to locate the
manifest.
To add registry support, a workaround in the local module storage was
added to record the subdirectory containing the module source from
within the archive file. Here we replace that temporary implementation
with the full manifest needed to record the necessary module metadata
for module loading.
In order to support versioned modules, the actual stored version needs
to be recorded. This can't be derived from the configuration, because
the configuration only contains the constraints, and at load time we need
to be able to enumerate the stored modules and all versions in order to
resolve them.
While the local storage key will be derived from the source and version,
that information is lost once it's hashed. While the entire storage
layer could be replaced to encode the needed data in the path itself,
this provides a minimal change to work with the existing storage code.