Add `long long` support to `Print::print`

The `Print` class in ArduinoCore-API has `print` functions with `long long` and `unsigned long long` parameter types:

https://github.com/arduino/ArduinoCore-API/blob/0f4e57ea193a00163ae59f0f0ff478feae7eb5db/api/Print.h#L73-L74

```cpp
size_t print(long long, int = DEC);
size_t print(unsigned long long, int = DEC)
```

https://github.com/arduino/ArduinoCore-API/blob/0f4e57ea193a00163ae59f0f0ff478feae7eb5db/api/Print.h#L87-L88

```cpp
size_t println(long long, int = DEC);
size_t println(unsigned long long, int = DEC);
```

This core's `Print` class does not:

https://github.com/arduino/ArduinoCore-avr/blob/master/cores/arduino/Print.h
https://github.com/arduino/ArduinoCore-avr/blob/master/cores/arduino/Print.cpp

### Additional context

#### Additional requests

- https://github.com/arduino/ArduinoCore-avr/issues/194
- https://github.com/arduino/ArduinoCore-avr/issues/194#issuecomment-222361044
- https://github.com/arduino/ArduinoCore-avr/issues/194#issuecomment-321053600
- https://github.com/arduino/ArduinoCore-avr/issues/347#issue-639975859

#### Related

- https://github.com/arduino/Arduino/pull/6608
- https://github.com/arduino/ArduinoCore-avr/pull/329

Start by comparing cores/arduino/Print.h and cores/arduino/Print.cpp with the ArduinoCore-API declarations linked in the issue. Trace the existing print and println overloads, then verify that both signed and unsigned long long parameters are supported with the requested base behavior. Done means the AVR Print class exposes and handles all four overloads consistently.

Written by the indexing model from the issue text.