[WIP][V1.20.0] Progress towards tablet support

This update aims to introduce some features that will make tablet support easier in the future. Tablet support will like require multiple releases in order to support fully as it is difficult to craft both an optimal phone and tablet experience within the same app. I will aim to add some tablet support here or there in the next several releases.

The biggest changes planned for this release are making screens more dynamic and responsive so they can handle different screen sizes and layouts better, adding a screen classification system to detect what type of layout would work best given the screen dimensions and the introduction of the navigation rail, a navigation bar that will be anchored on the left side instead of the bottom.

All of this is in the works at the moment. So far the idea will be to have the app classify the screen then decide whether to use the navigation rail based on that classification. This will be where the responsive screen layouts will come in so they can support neither a menu at the bottom or on the side with ease.

Changes so far:

• Systematically fix incorrect scores for good. This update moves voting invalidation logic to the core (where API calls are made) so this should systematically fix all inconsistent/outdated score issues. Note that this change will not affect caching. The app will continue to use the cache when appropriate. This fix is for cases where the app has gotten data that is fresher than the cache but vote numbers from the cache are still used.
• Added navigation rail. Navigation rail is like the bottom menu but it's on the left side instead. This rail is used instead of the bottom menu if the app detects the device screen is very wide (eg. if the devices is in landscape).
• Added option to toggle navigation rail.
• Added support for the new "listing type": Moderator view. The app has had support for a moderator feed however this was a client side hack. Since Lemmy v0.19 introduced this feed for real, the client side hack will be removed. What this means is that the moderator view will stop working on servers running Lemmy v0.18 or below. Please let me know if this is a concern to anyone.
• Improved the token expired experience.
• Improved the performance of account switching. After the per-account preference change, account switching has become a lot slower due to having to reapply all settings. The new account switcher only applies settings that have changed to improve account switching performance.
• Fixed a bug where sometimes video previews are not shown when they should be.