Enable oak-run indexing to connect to secondary node in Mongo replica set

With OAK-6353 support for document order traversal based indexing has been added. Currently it connects to Mongo primary.

We need to test and validate if it can be made only to connect to Mongo secondary for below 2 cases

1. Pre created checkpoint - Here checkpoint is created already and then oak-run only connects to Mongo secondary
2. Online indexing - Here oak-run would also create checkpoint. However it would need to be ensured that when it performs the document order traversal query that query is handled by Mongo secondary and oak-run logic ensures that secondary node has the created checkpoint