store: use Txn instead of Batch

Methods like `DeleteTo` do multiple deletions underneath that have to be done atomically. This is currently done via Batching, however, Batches [do not guarantee](https://github.com/ipfs/go-datastore/blob/bee84ceeb277b14249d1ac4297860fa7e52556f4/datastore.go#L97-L103) atomicity while transactions do.

Basically, the issue is to identify other places like above where the transaction should be used instead and make it so

Start by locating DeleteTo and other datastore operations that perform multiple deletions or writes through Batching. Compare those call sites with the datastore transaction API, then verify that every operation requiring atomicity uses Txn rather than Batch and preserves its existing behavior.

Written by the indexing model from the issue text.