The valid DatabaseVersion will be provided later through ComparableDatabaseVersion::setVersion.

This task completes the work started on SERVER-56908: the CatalogCache needs a way to create ComparableDatabaseVersion placeholders (i.e. only have the values captured from the atomics) that will be filled later once it gets the results from the loader.

SERVER-56908 assumed that a ComparableDatabaseVersion create with an empty-constructed DatabaseVersion would be enough. However, in some situations these placeholders don't get a valid version (BF-21215, mainly when the namespace is not found) and in this case the execution violated one important invariant: each DatabaseVersion has a valid uuid.

I evaluated other alternatives such as adding a method to check whether a DatabaseVersion but concluded that the proposal above is the less bad.