Create migration scripts to change from `akka_` schema prefix to `pekko_` prefix

This persistence plugin used to store data in databases with the `akka_` prefix but it has been changed to `pekko_`. A migration script should be provided to change this prefix for people coming from `akka_`

No files or tests are named. Start by locating the persistence plugin's database schema definitions and any existing migration mechanism; confirm how journal and snapshot tables use the prefix. Done means providing migration scripts that change the relevant akka_ schema names to pekko_ for existing users.

Written by the indexing model from the issue text.