Investigate whether `SycnTransaction` and `BufferedTransaction` can be removed in favour of `db/pebble/transaction.go`

[IronGauntlets]

Most likely there will only be one DB hence the SyncTransaction and BufferedTransaction abstractions may not be required. Instead, we should rely on the underlying DB implementation to provide the required functionality. Pebble already has a concept of Batch which is intended to batch multiple writes together before flushing to disk. The SyncTransaction explicitly uses a mutex to control the write and read operations, this should be ensured by the underlying db without further abstractions.