Remove expired caches.

If you split the cache file name in two:
Say 8 chars of md5 of the filepath and then the last 8 chars are md5 of esm version, config, mtime, etc. Then you can detect and remove old entries that start with the first 8 but don't have the current last 8.

No file, test, or entry point is named. Start by locating the cache-file naming and cleanup logic, then inspect how filepath, ESM version, config, and mtime contribute to the current cache identity; done means obsolete entries for the same filepath can be detected and removed without affecting the current entry.

Written by the indexing model from the issue text.