Backgrounds for "Circles" intro sequence

[N0Y0U2114]

Created folder "Texture/Intro/Circles" to store circles assets (following example set by assets for "Welcome" Intro sequence)

Assets gotten from an earlier release of osu-resources

[BashhScriptKid]

I believe there should be a valid reason why should it be added back in the first place

Not like it was removed for no reason either

[N0Y0U2114]

addresses ppy/osu#30957
Im making a follow up pull request implementing the circles background with that intro sequence

[N0Y0U2114]

I believe there should be a valid reason why should it be added back in the first place

Not like it was removed for no reason either

I did some digging and it kinda was removed for no reason

The timeline goes:
-Intro sequences got added. "Welcome" already used its own background.
"Triangles" didn't have a background yet, so both it and circles used its background (which was set as the default).

-Triangles got its own background, and this was set to the new default. The old images were replaced with the new ones.
The only changes were the image count was increased by 1, and the images were replaced.

Because they both used the default, circles never got its added because of either an oversight, or because the new background was being implemented quickly.