Fix: Allow HardwareI2C::requestFrom to return values > 256

[aentinger]

Changing return type of requestFrom from uint8_t to size_t allows the function to return the correct amount of bytes read (since internally it's already a size_t which is downcast to a uint8_t upon returning it).

Merging this PR is a pre-condition for merging arduino/ArduinoCore-API#132.

@facchinm Let's coordinate to get this done.

[github-actions]

Memory usage change @ 439eca3

Board	flash	%	RAM for global variables	%
arduino:mbed:envie_m4	0 - 0	0.0 - 0.0	0 - 0	0.0 - 0.0
arduino:mbed:nano33ble	0 - 0	0.0 - 0.0	0 - 0	0.0 - 0.0

Click for full report table

Board	libraries/Scheduler/examples/MultipleBlinks flash	%	libraries/Scheduler/examples/MultipleBlinks RAM for global variables	%	libraries/doom/examples/Doom flash	%	libraries/doom/examples/Doom RAM for global variables	%	libraries/KernelDebug/examples/KernelDebug flash	%	libraries/KernelDebug/examples/KernelDebug RAM for global variables	%	libraries/Portenta_SDCARD/examples/TestSDCARD flash	%	libraries/Portenta_SDCARD/examples/TestSDCARD RAM for global variables	%	libraries/Portenta_Video/examples/Envie_video_coreboot flash	%	libraries/Portenta_Video/examples/Envie_video_coreboot RAM for global variables	%	libraries/PDM/examples/PDMSerialPlotter flash	%	libraries/PDM/examples/PDMSerialPlotter RAM for global variables	%	libraries/ThreadDebug/examples/ThreadDebug flash	%	libraries/ThreadDebug/examples/ThreadDebug RAM for global variables	%
arduino:mbed:envie_m4	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0
arduino:mbed:nano33ble	0	0.0	0	0.0																	0	0.0	0	0.0	0	0.0	0	0.0

Click for full report CSV

Board,libraries/Scheduler/examples/MultipleBlinks<br>flash,%,libraries/Scheduler/examples/MultipleBlinks<br>RAM for global variables,%,libraries/doom/examples/Doom<br>flash,%,libraries/doom/examples/Doom<br>RAM for global variables,%,libraries/KernelDebug/examples/KernelDebug<br>flash,%,libraries/KernelDebug/examples/KernelDebug<br>RAM for global variables,%,libraries/Portenta_SDCARD/examples/TestSDCARD<br>flash,%,libraries/Portenta_SDCARD/examples/TestSDCARD<br>RAM for global variables,%,libraries/Portenta_Video/examples/Envie_video_coreboot<br>flash,%,libraries/Portenta_Video/examples/Envie_video_coreboot<br>RAM for global variables,%,libraries/PDM/examples/PDMSerialPlotter<br>flash,%,libraries/PDM/examples/PDMSerialPlotter<br>RAM for global variables,%,libraries/ThreadDebug/examples/ThreadDebug<br>flash,%,libraries/ThreadDebug/examples/ThreadDebug<br>RAM for global variables,%
arduino:mbed:envie_m4,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0
arduino:mbed:nano33ble,0,0.0,0,0.0,,,,,,,,,,,,,,,,,0,0.0,0,0.0,0,0.0,0,0.0