TuktuDB generator should read from node that contains the bucket

[ErikTromp]

A TuktuDB is entirely stored on a single node, though different buckets exist on different nodes. Now, the TuktuDB read generator is ran on the node it is initiated on, regardless of where the bucket's data is actually stored. We should instead optionally have the generator run on the node that holds the bucket to avoid getting data from one node to another.