Allow configuring Wire.h buffer size

[flaviut]

This is needed since in some applications, we need much much larger buffers.

See emporia-vue-local/emporia-vue2-reversing#1 (comment)

[flaviut]

After further investigation prompted by @Maelstrom96's comments elsewhere, this isn't sufficient to allow for the 284 byte payloads we need to handle.

We'd also need #ifs to make sure that the various types aren't uint8_t, but are promoted to uint16_t when the size of the payload is increased. I'd be happy to do that work, if the maintainers would chime in on if that'd be an acceptable solution, or if it'd be better to fork the Wire library.

[flaviut]

Whoops! I shouldn't be programming before fully waking up! I'm actually looking to do this on the ESP32, not ESP8266.

I'd be happy to port any changes here too, please re-open this if you'd like me to do that.

[mcspr]

See #8388 espressif/arduino-esp32#5172
Might be a good idea to share the name of the setting

[d-a-v]

Using int16 or even int32 sometimes generate less code / is faster than when using int8, on this architecture.