Add childrenIter method to API nodes - #64302

async function *visitNodeForFirstAnyChild(node: Node): AsyncGenerator<Node | undefined, Node | undefined, Node | undefined> {
    for (const n of node.childrenIter()) {
        const t = await checker.getTypeAtLocation(n);
        if (t.flags & TypeFlags.Any) { return n; }
        const res = yield* visitNodeForFirstAnyChild(n)
        if (res) { return res; }
    }
}
const res = (await visitNodeForFirstAnyChild(stmt).next()).value;
assert.strictEqual(res!.getText(), "p: any");