Feed refresh operation should query network state before starting

[opusforlife2]

Checklist

• I made sure that there are no existing issues - open or closed - which I could contribute my information to.
• I have read the FAQ and my problem isn't listed.
• I'm aware that this is a request for NewPipe itself and that requests for adding a new service need to be made at NewPipeExtractor.
• I have taken the time to fill in all the required details. I understand that the feature request will be dismissed otherwise.
• This issue contains only one feature request.
• I have read and understood the contribution guidelines.

Feature description

It's a small optimisation, but the app should check for an active internet connection before attempting to refresh the feed. It should show a toast saying Internet isn't available if that is the case.

Why do you want this feature?

When you have Internet turned off on your device, and try to refresh the feed, the app actually goes through the entire list of subscriptions and fails to load new videos from each one.

It's not an error from the app's side, so the UI shouldn't behave as if something went wrong. A toast punting the blame towards the lack of internet connection would make things clearer.

Additional information

No response

[opusforlife2]

Related: #7651