Fix alignment issue of beatmap background for non-widescreen storyboard

[Rudicito]

• Similar to closed PR #14001
• Fix #2086
• Fix #28928

To fix the issue, this PR adds the beatmap background as a storyboard element in the "Background" layer to resolve the alignment issue IF the storyboard is non-widescreen (and other conditions see NeedSetBackgroundInStoryboard in Storyboard.cs)

I chose this approach based on peppy's recommendation on closed PR #14001 that tried to fix the same issue.

Before PR:

https://github.com/user-attachments/assets/ba20dba7-1882-436b-a9d3-8507d7b02757

After PR:

https://github.com/user-attachments/assets/71a427e6-fd3c-44e8-abab-f70f7ab50d48

Beatmap used in video : https://osu.ppy.sh/beatmapsets/58246

[tadatomix]

I'm sorry, if it's not a good place to ask, but I don't see this question raised anywhere here. How is it going to behave when "Background blur" is set to value, different from 0%?

[Rudicito]

@tadatomix It's not going to do anything, I don't think it should?

[tadatomix]

@tadatomix It's not going to do anything, I don't think it should?

@Rudicito Sorry, I needed to have a better phrasing for this question. I mean, some of the beatmaps (e.g. La Di Da) has a blurred background in storyboard, already. So what I'm asking is will "Background blur" value be applied to resized to 4:3 beatmap background or not?

[Rudicito]

No, "Background blur" will not be applied to the resized 4:3 background.

[tadatomix]

No, "Background blur" will not be applied to the resized 4:3 background.

Alright. Thank you for the answer.

[Rudicito]

I think I have to re-request review? Sorry if not, first time doing this.