KAFKA-19400: Update AddRaftVoterRequest RPC to version 1

[kevin-wu24]

Add the ackWhenCommitted boolean field to the AddRaftVoterRequest RPC, and bump the RPC's version to 1.

• The default value of ackWhenCommitted is true, and in this case the leader will return a response after committing the VotersRecord generated by the RPC.
• If ackWhenCommitted == false, the leader will return a response after writing the VotersRecord to its own local log.
• Add unit tests in KafkaRaftClientReconfigTest