Summary:
Move ReplicationInfoPB to `common_net.proto` because it is used in more than master, and future diffs will add even more logic accessing it from PG.

**Upgrade/Rollback safety:**
Moving a proto across namespaces is safe, as long as it is not used in any `Any` type messages (which ReplicationInfoPB is not).
Jira: DB-14387

Test Plan: `./yb_build.sh release --cxx-test integration-tests_replication_info_upgrade-test`

Reviewers: hsunder

Reviewed By: hsunder

Subscribers: yql, ybase

Differential Revision: https://phorge.dev.yugabyte.com/D40826