Fix GameHost.Collect() being called twice on android

[Susko3]

Depends on (to have identical behaviour):

• Use onTrimMemory() instead of onLowMemory() on Android libsdl-org/SDL#9654
• New SDL3-CS build.

SDL sends us a SDL_EVENT_LOW_MEMORY when Android's onLowMemory() handler fires. o!f handles this event and calls GameHost.Collect(). We also have our own handling in onTrimMemory(). Depending on how android handles those two functions, we may collect memory twice.

I think it makes more sense to just have SDL_EVENT_LOW_MEMORY handling, and not have custom logic just for android.

This PR was originally meant to pick out the useful parts from https://github.com/ppy/osu-framework/pull/6269/files#r1584189904, but I've since realised SDL already sends us a low memory event that we handle.

[hwsmm]

I actually noticed it before, so I removed it in my cleanup commit, but I guess some changes after mine added it back?

Though I think I should have added a comment in the commit to make sure it was intended.

[peppy]

i guess we have a new sdl3-cs build now?

[bdach]

Probably be best to get another sdl3-cs package out to get the fix for #6299.

[Susko3]

I've bumped ppy.SDL3-CS.Android version to match ppy.SDL3-CS (they should always match, but it was missed). This includes the SDL3 change required for this PR.

Perhaps the ppy.SDL3-CS.Android package should depend on ppy.SDL3-CS of the same version. Bumping only one would cause package upgrade/downgrade build failures.