Automatically download episodes to the watch

### What problem does this address?

Often the watch app will have poor or no network connection when I want to listen to an episode. If I didn't remember to download the episode ahead of time that means I either have to (a) remember to download the episode ahead of time or (b) if I have some network connection, use the slow network connection to either listen to the episode by streaming it (likely with a lot of choppiness while the episode buffers) or waiting a long time for the episode to download.

### What is your proposed solution?

It would be great to have a way to set up the watch to automatically download some episodes when a wifi connection is available. I'm not sure what the best implementation of this would look like, but some possibilities include:
1. Having all episodes of a given podcast download automatically
2. Having all episodes of a given filter download automatically
3. Having the currently playing and next first N episodes in the Up Next queue download automatically

### Did you search for existing feature suggestions?

- [X] I have searched for existing feature suggestions.

[Internal feature request](https://pocketcastsideas.wordpress.com/2023/07/26/wear-os-auto-downloads/)

Start with the watch app's download behavior and its handling of Wi-Fi availability, then compare the podcast, filter, and Up Next queue options described in the issue. No files or tests are named, so the first task is to locate those entry points. Done would mean an agreed automatic-download behavior is implemented for the selected episodes.

Written by the indexing model from the issue text.