samples: pmci: mctp: Add I2C+GPIO bus owner sample

Adds a sample application that can act as the bus owner using
i2c+gpio mctp binding.

Provides an overlay for the frdm-mcxn947 using JP8 pins for i2c and
gpio.

It attempts to send a "ping" message to all endpoints while accepting
string messages from endpoints to print out.

Signed-off-by: Tom Burdick <thomas.burdick@intel.com>