raft: Retrieve memberId and partitionKey for replicas which are promoted to leader

This MR !7942 focuses on replicas that are self-bootstrapped or are created on a remote node. There appears to be a third scenario where:

• A replica (memberID 2) is part of the cluster and subsequently becomes the leader through Raft leader election.
• The routing table is updated to reflect the new leader, and the partition is closed.
• When a new request arrives, it is directed to replica two, which begins receiving client (Rails) requests without a partitionInfo context (which contains partitionKey and memberID).

In this case, while starting the partition, we would need a way to retrieve the partitionKey and memberID, which were initially used by the replica before it became the leader.