[Code health] Fixes and cleanup of `LocalMutationSyncWorker`

Code health improvements which came up while fixing #2129:

Recommended:

- [ ] Warn and ignore mutations not belonging to current signed in user (#2237)
- [ ] Wrap `remoteDataStore.applyMutations` in `MutationRepository`
- [x] #2236

Nice to have:

- [ ] Log an error if "create" submissions were enqueued after "edit" submissions
- [ ] Replace `MutationRepository.markAs..` methods with `saveMutationsLocally` and helper on `Mutation`
- [ ] Improve naming of `finalizePendingMutationsForMediaUpload()` and `finalizeDeletions()`
- [ ] Only call `enqueueSyncWorker()` if media uploads are pending for this LOI
- [ ] Extract business logic into `UserDataUploadUseCase`
- [ ] Move `getPendingOrEligibleFailedMutations()` into repository (#2237)

Not needed:

* ~Stop marking all mutations for an LOI as `IN_PROGRESS` at once. Instead, process each mutation individually, and set `IN_PROGRESS` before actually processing.~
* We do this because we process mutations in batch.
* ~Abort updates to this LOI if any mutations were unsuccessful~
* Mutations are applied as a batch write, which are atomic.

@scolsen Breaking these out so we can keep moving forward