AsyncTask is deprecated, adjust the guides to reflect?

We may or may not need to make changes to these guide based on the news https://www.xda-developers.com/asynctask-deprecate-android-11/

- https://guides.codepath.com/android/Creating-and-Executing-Async-Tasks - Could be kept as is but updated to reflect the deprecation and linking to an updated guide which presents the alternative.
- https://guides.codepath.com/android/Sending-and-Managing-Network-Requests - Probably needs to be adjusted to use the simplest possible alternative when showing the "Hard" way
- https://guides.codepath.com/android/Managing-Threads-and-Custom-Services - Thankfully not too much is AsyncTask related here, but probably good to review for accuracy
- https://guides.codepath.com/android/Starting-Background-Services - Thankfully not too much is AsyncTask related here, but probably good to review for accuracy

The good news: Many of these only lightly touch on AsyncTask. I don't think at least guides wise we will have to make huge changes.