Implement placement driver API

    /**
     * Returns a future for the primary replica for the specified replication group whose expiration time (the right border of the
     * corresponding lease interval) is greater than or equal to the timestamp passed as a parameter. Please pay attention that there are
     * no restriction on the lease start time (left border), it can either be less or greater than or equal to proposed timestamp.
     * Given method will await for an appropriate primary replica appearance if there's no already existing one. Such awaiting logic is
     * unbounded, so it's mandatory to use explicit await termination like {@code orTimeout}.
     *
     * @param replicationGroupId Replication group id.
     * @param timestamp Timestamp reference value.
     * @return Primary replica future.
     */
    public CompletableFuture<ReplicaMeta> awaitPrimaryReplica(ReplicationGroupId replicationGroupId, HybridTimestamp timestamp) {
        return CompletableFuture.completedFuture(null);
    }

    /**
     * Same as {@link PlacementDriverManager#awaitPrimaryReplica(ReplicationGroupId, HybridTimestamp)} despite the fact that given method
     * won't await for an appropriate primary replica appearance if there's no already existing one, in that case null will be returned.
     *
     * @param replicationGroupId Replication group id.
     * @param timestamp Timestamp reference value.
     * @return Primary replica future.
     */
    public CompletableFuture<ReplicaMeta> getPrimaryReplica(ReplicationGroupId replicationGroupId, HybridTimestamp timestamp) {
        return CompletableFuture.completedFuture(null);
    }