getFolder does not return fully populated ArchiveRecords

[slifty]

This is, to some extent, a known behavior however it is not ideal.

First: it would be better if the ArchiveRecord children returned in a getFolder result contained Files. This would prevent our clients from having to make one-new-API-call per ArchiveRecord in contexts where they want the file associated with a given ArchiveRecord.

Second: if we DO keep the current behavior, it needs to be clearly communicated via types that Folder.archiveRecords will never have populated files. Otherwise you get people writing code expecting files!