Respect Series Thumbnail Option

[linkRace]

Changes
UserPreferences.Companion.getSeriesThumbnailsEnabled() was not being passed into the ItemRowAdapter, just a hardcoded false, which meant that the episode thumb was being displayed instead of the series thumb. I changed the preferParentThumb check to look for parentBackdropImages first then parentImages then seriesThumbImage, based on what I saw on the web requests.

Code assistance:
Asked Claude to show me where the settings were getting loaded.

Issues:
#3195

Images:
Current State:

New State:

[nielsvanvelzen]

Using the preference in more places were it makes sense is fine while we still have this setting. We shouldn't use the backdrops as thumbnails though, they're not meant for that purpose.

[linkRace]

Using the preference in more places were it makes sense is fine while we still have this setting. We shouldn't use the backdrops as thumbnails though, they're not meant for that purpose.

I was just using what the web app uses for them when you have the setting enabled there to maintain consistency. If they're not meant for that purpose, why is that what the web is using?

[nielsvanvelzen]

If they're not meant for that purpose, why is that what the web is using?

I'm (fortunately) not responsible for how the web client behaves. But a backdrop is, like the name implies, meant as a backdrop (e.g. background/wallpaper/screensaver etc.) and not a thumbnail. The appropriately named thumb(nail) image type exists for that use-case.

[linkRace]

The trouble is that many shows just don't have a series thumbnail, which results in spoiler episode thumbnails being displayed if there isn't one whereas a backdrop solves that issue.
A separate option to say Use backdrop when no Series Thumb exists seems like clutter to me when I would think most users like myself checking the Prefer series thumbnail option would expect the behavior I've written here to be what happens.
How would you recommend I proceed given that just using the series thumbnail doesn't solve the intent behind this PR? I have changed it currently to use the series thumbnail where it exists before falling back to the backdrop, but again that only solves a few shows.