[wasm][debugger] Support indexing Dictionary by object key #76014

Tests: in DebuggerTests.EvaluateOnCallFrameTests.EvaluateUserDefinedIndexingByNonIntLocals uncomment lines:

// ("f[aDecimal]", TNumber(3))

and fix. Decimal is treated as an object. We can handle indexing by it e.g. by adding in GetElementIndexInfo in case of (arg.Expression is IdentifierNameSyntax)

// indexObject={
//   "type": "object",
//   "value": null,
//   "description": "3.34",
//   "className": "System.Decimal",
//   "objectId": "dotnet:valuetype:9",
//   "isValueType": true
// }
                        if (indexObject["type"].ToString() == "object") // e.g. System.Decimal behaves this way
                        {
                            elementIdxStr.Append(indexObject["description"].ToString()); // or resolving value
                        }
                        else
                        {
                            elementIdxStr.Append(indexObject["value"].ToString());
                        }

But when one class has multiple indexers like we have in our tests, then in Task<JObject> Resolve(ElementAccessExpressionSyntax elementAccess, Dictionary<string, JObject> memberAccessValues, JObject indexObject, List<string> variableDefinitions, CancellationToken token) we'll get multiple "get_Item" methods. In case of Decimal, it is sent as 4th method out of 6 and the 2nd method is public bool this[string key3] => key3.Length > 3;. We are trying all possible methods till one works (does not throw an exception) and by coincidence the boolean-returning method does not throw. That's why we resolve a wrong value by mistake. We return

{
  "type": "boolean",
  "value": true,
  "description": "true",
  "className": "System.Boolean"
}

instead of "number" 3.