Event Sourcing based dataModel Rewrite (ADR 0011)

[Al12rs]

Rewrite app backend to log user operations as series of events that can be undone, rather than series of immutable loadout snapshots. See ADR 0011 for more information.

[Al12rs]

Additional changes from #719 PR feedback:

• [x] Rename FromArchive to StoredFile. (#719)
• [x] Rename DownloadRegistry to FileOriginRegistry. (#719)
• [x] Rename ArchiveManager to FileStore. (#719)
• [ ] Consider adding a trait describing files that were Ingested, or some other way to distinguish files that were ingested from files originated from a downloaded mod (and thus can potentially be downloaded again vs only available locally).
• [ ] Attempt to move to a more functional system than the current Alter one (which had side effects of saving to db and updating loadout markers).
• [ ] Limit and make clear which interfaces have the power to mutate things (save stuff in db, update current index, create checkpoint snapshots etc).
• [ ] Rename DataStoreId nomenclature for loadout revisions ids, use something clearer like LoadoutRevId or SnapshotId.