ParsedDataPersistence

Persisting a parsed-data store to, and restoring it from, its backing files.

Separate from {\StubTests\Framework\Storage\ParsedDataWriter} because the two have different audiences: a parser fills a store, while only the cache-generation paths decide when it is written to disk. Keeping save() and load() out of the type handed to read-only consumers is the point of the split — a validator that receives a store for querying should not be able to overwrite the committed cache.