Cancel slot migration in case of OOM errors on target node

[adiholden]

When migrating slots data from one shard to another we can get OOM when adding the migrated data on the target node. In such case we should cancel the slot migration.

[adiholden]

More details of the flow
in incoming_slot_migration.cc we ClusterShardMigration::Start we read commands from the socket - tx_reader.NextTxData and execute the command to add the data on the target node - ExecuteTx.
In this flow if command execution returns OOM (add return value to ExecuteTx), we should cancel the migration

[mkaruza]

Fixed with #5000