[Tests] Need improve custom rule for allowing skip return type declaration for callbacks

[MaxGraey]

Will be great write this for internal tests:

var result = source.filter(value => value > 2); // linter with custom rule not happy currently

instead:

var result = source.filter((value: i32): bool => value > 2);

Code part in "lib/lint/src/rules/asTypeRule.ts" which should be changed:

...
  visitArrowFunction(node: ts.ArrowFunction) {
    this.checkFunctionReturnType(node);
    super.visitArrowFunction(node);
  }
...

But still guard for return type for rest cases