Extends String to print 64-bit integers

[SuGlider]

Description of Change

This PR adds support to long long (64 bits) numbers to Arduino String Class.

Tests scenarios

Tested with this sketch:

void setup()
{
  Serial.begin(115200);
  Serial.println();

  // highest signed long long 2^63 - 1 = 9223372036854775807
  // highest unsigned long long 2^64 = 18446744073709551615
  signed long long ll = -9223372036854775807;
  unsigned long long ull = 18446744073709551615;
  
  String ss(ll);
  Serial.println(ss);
  String uss(ull);
  Serial.println(uss);

  String txt("This is the highest signed long long: ");
  txt += -ll;
  Serial.println(txt);
}

Related links

Fixes #5672