Declaring abs define in Arduino.h breaks compatibility with TensorFlow Lite

Why is `abs` defined in the Arduino.h for this core?

https://github.com/arduino/ArduinoCore-mbed/blob/682a054fb9769066571ab046b200b2a30b18c11a/cores/arduino/Arduino.h#L70

This conflicts with `std::abs` usage f.e. in TensorFlow Lite. I think this has happened before in other cores, as there's a provision in TF already for this:

https://github.com/tensorflow/tensorflow/blob/845adc40a653b311f4df2c273b22de7e175a93a1/tensorflow/lite/type_to_tflitetype.h#L18

But it still required us to patch this undef in at a later point as well when porting EI to Portenta.

Start in cores/arduino/Arduino.h around line 70 and inspect how abs is declared. Compare that declaration with the std::abs usage and the TensorFlow Lite compatibility references linked in the issue; done means the Arduino core no longer causes the reported TensorFlow Lite compatibility conflict.

Written by the indexing model from the issue text.