Adds Wire::setBufferSize function

[SuGlider]

Description of Change

Adds a new Wire (I2C) functionality to set the RX/TX buffer size and change it any time in the sketch.
Some I2C devices and sensors may require a bigger buffer for its transactions.

Tests scenarios

#include "Wire.h"

void setup() {
  Wire::setBufferSize(512);
  Wire::begin();  // as I2C Master
}

void loop() {
}

Related links

Fixes #6967
Fixes #7042

[r-downing]

If the size doesn't need to be changed at runtime, perhaps this could be done with a template size, so you don't have to use up more heap memory?

template <size_t desiredCapacity = DEFAULT_SIZE>
class TwoWire: public Stream
...
    uint8_t txBuffer[desiredCapacity];

edit - nevermind, this would be breaking before c++ '17, as you would be required to put the <>

[SuGlider]

Arduino APIs use to be "user proof" also... So creating an API with all necessary checks is safer.

[P-R-O-C-H-Y]

Looks good, will test tomorrow :) take a look on my comments @SuGlider

[P-R-O-C-H-Y]

LGTM :) Good job @SuGlider