In this commit, we follow up our previous migration to reset our synced
block to our birthday block with another migration to drop our
transaction history. We'll need to do this to ensure that the
transaction store matches the exact state of our outputs on-chain to
prevent inadvertently crafting any invalid transactions.
In this commit, we add an implementation of the recently introduced
migration.Manager interface for the transaction manager. With this,
we'll now be able to only expose the things required for the migration
to happen, but have the actual migration logic live at a much higher
level.
There are no existing migrations for the transaction manager, but since
the latest version was already defined as 1, we'll start from there to
be backwards-compatible.
