[NXT - help wanted]: Implement I2C module

[laurensvalk]

We don't have an I2C driver for NXT yet.

We would need a file called i2c_nxt.c that implements the equivalent functionality of i2c_ev3.c. Unlike the EV3, the NXT does not use a co-processor for I2C, so everything can just go into this one file.

Almost everything should already be here, which can be used as inspiration. By implementing it as above, we'd get non-blocking versions. Portions of this API can be copied rather than attempting to call this blocking API.

When this low-level driver is implemented, it can be tested with the pybricks.iodevices.I2CDevice class that is already enabled.