migration30: add migration to convert old revocation logs

This commit adds the migration that's used to convert the old revocation
logs into the new format. The migration is fault-tolerant, meaning the
process can be interrupted and the migration will pick up what's left
when running again. We also cap how many records to be processed in each
db transaction to prevent OOM.

channeldb/log.go

@@ -8,6 +8,7 @@ import (
 	"github.com/lightningnetwork/lnd/channeldb/migration13"
 	"github.com/lightningnetwork/lnd/channeldb/migration16"
 	"github.com/lightningnetwork/lnd/channeldb/migration24"
+	"github.com/lightningnetwork/lnd/channeldb/migration30"
 	"github.com/lightningnetwork/lnd/channeldb/migration_01_to_11"
 	"github.com/lightningnetwork/lnd/kvdb"
 )
@@ -38,5 +39,6 @@ func UseLogger(logger btclog.Logger) {
 	migration13.UseLogger(logger)
 	migration16.UseLogger(logger)
 	migration24.UseLogger(logger)
+	migration30.UseLogger(logger)
 	kvdb.UseLogger(logger)
 }