moved mac storage to singleton, tried to reduce response time

with these changes, the time until the client receives an ack from the host is ~100ms. i didn't have any issues storing/retrieving the mac address of the host in testing. Same for connecting a new client to the host

Apparently it's possible to increase the datarate used by espnow, however this could mess with reliability. i believe we should first try to decrease the amount of messages sent/reduce message size.