FunC reports overflow in expressions that would not produce overflows at runtime

[jeshecdom]

Using the expression fuzzer, we have found a couple of compilation examples where FunC reports an overflow on expressions that would not produce an overflow if executed.
In fact, when such expressions are executed in the interpreter, the interpreter does not report an overflow and produces the correct result.

contract A {

   get fun test(): Int {
      // 2^256 - 45
      let int1 = 115792089237316195423570985008687907853269984665640564039457584007913129639891;
      // false case will execute, and it is less than 2^256-1
      let res = (int1 != int1) ? (int1 + int1) : 33321583122581966542555556347793674561846130234625845898374435335324439320969;  
      return res;
   }
}

with error message:

> A: tact compiler
> A: func compiler
FunC compilation error: cannot generate code for function `$A$_fun_test`:
/test_A.fc:56:43: error: integer overflow
      int $res = (($int1 != $int1) ? ($int1 + $int1) : 33321583122581966542555556347793674561846130234625845898374435335324439320969);
💥 Compilation failed. Skipping packaging

And this other example:

contract A {

   get fun test(): Int {
      // 2^255
      let int1 = 57896044618658097711785492504343953926634992332820282019728792003956564819968;
      // true case will execute
      let res = int1 == int1 ? int1 : int1 + int1;  
      return res;
   }
}

with similar error message:

> A: tact compiler
> A: func compiler
FunC compilation error: cannot generate code for function `$A$_fun_test`:
/test_A.fc:56:51: error: integer overflow
      int $res = (($int1 == $int1) ? $int1 : ($int1 + $int1));
💥 Compilation failed. Skipping packaging

This issue is related to div by zero issue #716, since that issue reports an example where FunC produces a div by zero error on an expression that would not produce a div by zero at runtime.