`streamInfo` and `channelInfo` have to be initialized, since the only
way to construct the class it to pass them. So we can remove the null
check boilerplate and make some of the accessors `NonNull`.
This change is in line with a recent change in how the play/pause button behaves in the player ui: if the buffering indicator is shown, it's still possible to toggle play/pause, to allow e.g. pausing videos before they even start.
This change was needed because on Android 13+ notification actions can't be null, and thus the buffering hourglass action wasn't shown.
Disable loading all tabs at once, since there can be many of them, and use default strategy of only keeping in memory the two tabs adjacent to the current tab.
Reduced memory footprint of FeedUpdateInfo objects. Those objects might stay around for a while and accumulate (up to BUFFER_COUNT_BEFORE_INSERT = 20 at the moment), so in order not to fill up the memory it's better to keep as little data as possible.
Previously ChannelInfo data was stored, causing ReadyChannelTabLinkHandler objects to be also stored uselessly (and those channel tabs contain prefetched JSON data which used ~700KB of memory).
The fix just involves removing some really outdated code (6 years ago) added in 33e29be7db (diff-38bd2cf1b92659b499c08e1cf6ac9ef384c7e13381b906f2f98c57cbb758756dR778) (blame: https://github.com/TeamNewPipe/NewPipe/blame/9318bb530619898c1e1f3f8a8c866f3d2e35ab0c/app/src/main/java/org/schabi/newpipe/detail/VideoItemDetailActivity.java#L778).
What that code did was setting the 'buddy' image to the uploader avatar as a placeholder, and then setting the actual image if it existed and after it had loaded.
That code remained there up until now, but now it doesn't make sense anymore, since Picasso already takes care of setting placeholders.
The problem is, starting from #10066 the actual uploader image is set before (not after) those lines of code, making them do the wrong thing, i.e. always overwrite the currently set image.
But then why did the channel avatar image work normally sometimes?
My guess is that since Picasso loads images in the background, when opening a video from scratch setting the placeholder still happened before Picasso finished loading the image.
However when the image is already cached it's loaded much faster and therefore setting the placeholder happens after, effectively hiding the loaded image.
