Fixes the root client-side failure causing
https://github.com/ppy/osu/issues/30415.
Thread of breakage is as follows:
1. `SongSelect` loads the carousel.
At this point, the ruleset is what the ambient ruleset would have
been at the time of pushing song select, so most likely it will
match the current ruleset.
Notably, the carousel is loaded with `AllowSelection == false`.
2. `OnlinePlaySongSelect` sets the ruleset to the one taken from
the relevant playlist item in `LoadComplete()`.
3. At any point between the previous and the next step, the user
changes the ruleset manually.
4. `SongSelect.carouselBeatmapsLoaded()` is ran, which calls
`transferRulesetValue()`, which calls `FilterControl.FilterChanged`.
But at this stage `Carousel.AllowSelection` is still false, so
the filter is not executed, but `pendingFilterApplication` is set
instead.
Unfortunately, the pending filter never gets applied after that.
The only place that checks that flag is `OnEntering()`, which at
this point has already ran.
To fix, move the `pendingFilterApplication` check to `Update()`, which
seems like the most obvious and safe solution.
Broke due to something changing in the way we handle realm things in the
carousel. The deselection happens in `updateBeatmapSet` so we need to
store / check the original selection before this occurs.
Doesn't seem this had test coverage? Probably implies that the overhead
of adding a test was very large, so maybe best to leave it that way.
Closes https://github.com/ppy/osu/issues/30163.
If I'm to be blunt, the decoupled stuff in song select makes my head
spin. I spent a solid 20 minutes thinking how I was going to fix this
one but then finally realised that generally most of the cause there
was the fact that `AdvancedStats` was seeing the new rulesets *before*
the "ensure global selected mods are valid for current ruleset" logic,
and so decided to just _delay_ that until the decoupled transfer
thingamajig happens.
I was honestly considering combining `BeatmapInfo`, `Ruleset`, and
`Mods` into one property on `AdvancedStats`. I figured I'd rather not
push my luck and try the baseline version first, but I honestly think
that direction is going to be required at some point to properly corral
all of the decoupled madness taking place in song select.
