consider fixing broken waiting on any filtered_like_collection.cached

[yashaka]

currently collection.cached does not have waiting built in...

under the hood we use .cached inside locators, so that's ok...

but there will be scenarios for the end user, where the use would want to cache elements after he waited for the correct collection size, for example via browser.all('.item')[:3].cached And here we may fail without waiting, that is pretty not consistent with normal selene's behavior...

[yashaka]

seems like pretty tough connected with #534