Handle Possible Throw When Branching on Abstract Value

[jwli229]

let x = global.__abstract ? __abstract("boolean", "true") : true;
let y;
try {
  if (x) {
    y = 1;
    throw Error();
  } else {
    y = 0;
  }
}
catch(e) {
}

On a branch based on an abstract value where one of the branches throws and the other doesn't (example above), a fatal error occurs since the result of the evaluation is a PossiblyNormalCompletion.
Prepack should handle the join of the branches in this case.

[NTillmann]

At the very least, the resulting error code should get some help text:
https://github.com/facebook/prepack/wiki/PP0001 is not yet populated.

[hermanventer]

PP0001 is currently used for errors that are generated the old way, via reportIntrospectionError. These errors should instead be generated by calling handleError directly, with specific error codes and relevant source locations.

[jwli229]

I can change the error handling.