Optional className: stringReleases the snapshot store(s) for a given class name, freeing their in-memory
call/string/value pools so they can be garbage-collected. The released store(s) are also
removed from the global registry; if needed again they are re-created and lazily re-loaded
from disk on the next getSnapshotStore. No-op when className is absent or no store
exists for it.
Call this between host test files to bound memory in a long-running worker (e.g. vitest
isolate: false). Make sure data has been flushed first.
name of the mocked class to release