MAINT: sparse: Stop supporting multi-Ellipsis indexing

[perimosocordiae]

Reference issue

This is the cleanup that we started warning about in gh-18540.

NOTE: We should not merge this until at least v1.13.0! I'll leave this in draft mode until then.

[rgommers]

NOTE: We should not merge this until at least v1.13.0! I'll leave this in draft mode until then.

Can you close this and reference it in the deprecation meta tracker issue (gh-15765) instead? Having a PR in the queue that's not mergeable for another year at least is a little annoying; it can be reopened when it's mergeable. We have folks that are good about going through the outstanding deprecations for every release.

[j-bowhay]

I already have this in the tracker so will reopen it when we start development on 1.13

[perimosocordiae]

Sounds good, thanks!

[h-vetinari]

1.12 has branched, so this is now fair game. :)

[j-bowhay]

@perimosocordiae diff seems reasonable but just wanted to check in before merging that you were happy with everything since it has been 6+ months since opening

[perimosocordiae]

Thanks, I just took another look and I'm happy with it.

[j-bowhay]

Not an expert in this part of the codebase but diff looks reasonable and CI is happy, thanks @perimosocordiae