For every peer expose through `getpeerinfo` RPC whether or not we selected them as HB peers, and whether or not they selected us as HB peers.

Suggestion by @gmaxwell.
#include <rpc/server.h>
#include <banman.h>
#include <clientversion.h>
#include <core_io.h>
#include <net.h>
#include <net_permissions.h>
#include <net_processing.h>
#include <net_types.h> 
#include <netbase.h>
#include <node/context.h>
#include <policy/settings.h>
#include <rpc/blockchain.h>
#include <rpc/protocol.h>
#include <rpc/util.h>
#include <sync.h>
#include <timedata.h>
#include <util/strencodings.h>
#include <util/string.h>
#include <util/system.h>
#include <util/translation.h>
#include <validation.h>
#include <version.h>
#include <warnings.h>
#include <univalue.h>