No SymbolId for function overloads

[mxsdev]

Looks like function overloads don't have symbols assigned to them.

For example in the following code:

function overload1(n: number) : string;
function overload1(ns: any) {
    return ns.toString();
}

The second overload1 has a symbol, but the first does not.

Let me know if anyone on the team is tackling this area right now, otherwise I can maybe try and take a crack at it.

Possibly related to #8039