api: Propagate async response through `toggleMessageStarred`.
api: Propagate async response through `toggleMessageStarred`.

`toggleMessageStarred` immediately returns void, not reporting the
success or failure of its async operation to its caller.

Instead, propagate its implementation's Promise<ApiResponse> upward.

vishwesh3/zulip-mobile,vishwesh3/zulip-mobile,vishwesh3/zulip-mobile,vishwesh3/zulip-mobile