`@TsIgnore` prevents interface members from being present on subtypes

[niloc132]

Using the tests currently in main, add @TsIgnore to NonJsTypeParent, and attempt to build - as this type was already omitted from the generated index.d.ts file, as I understand it it should have minimal impact.

However, after adding that, inherited members from TsInterfaceParent are no longer present:

    export class JsTypeGrandChild implements TsInterfaceParent {
        propertyFromA:string;

        constructor();

        doSomethingFromA():string;
    }

Expected:

    export class JsTypeGrandChild implements TsInterfaceParent {
        propertyFromA:string;
        propertyFromC:string;

        constructor();

        doSomethingFromA():string;
        doSomethingFromC():string;
    }