Change PTP master and slave to timeTransmitter and timeReceiver according to IEEE 1588g-2022

[haug-den-lucas]

Hello,

the IEEE 1588g-2022 amendment suggests to replace the terms master and slave in (g)PTP to timeTransmitter and timeReceiver.
I'd like to see this change reflected in the INET project.
If I get the okay from one of the INET maintainers, I'd change the code and showcases accordingly and create a PR myself.