Updating Table isLoading prop to be loadingState (#1902)
* Updating Table isLoading prop to be loadingState
allows us to have greater control over when to render the loading spinner (aka we do not show it when useAsyncList is performing a filter operation)
* adding test and fixing lint
* fixing stories and tests and using this.isLoading
looks like this.isLoading is kept up to date in TableLayout so using it instead of checking this.collection.body
