pagination: enforce nonNull on the inner type as well as on the list

[mfn]

Summary

• Based on Add support for non null type in pagination type #1012
• Fixes NonNull type for data in pagination and NonNull ListOf type #872

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Type of change:

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update
• Misc. change (internal, infrastructure, maintenance, etc.)

Checklist:

• Existing tests have been adapted and/or new tests have been added
• Add a CHANGELOG.md entry
• Update the README.md
• Code style has been fixed via composer fix-style

[99linesofcode]

@mfn it's good to see that this is merged. Will it be part of a new major release and if so, when do you expect that to ship?

[mfn]

I want to put out an RC2 soon and hope to include #1008 for it too.

[mfn]

#1008 is still a bit unclear, I've just put out 9.0.0-rc2.

The idea is to make the 9.0.0 stable release in a week latest.