fix(core): resolve PHPStan iterable type errors (#8732)

[Chucho-Kun]

Description
PHPStan errors were eliminated by reducing the baseline to 1200 errors as part of my contribution to the good first issue label
The modifications is in the branch fix/issue-8732-basemodel-types and were validated with the following command

composer phpstan:check -- --memory-limit=512M

[mergeable]

Hi there, Chucho-Kun! 👋

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[michalsn]

Thank you. Please omit any modifications related to Kint, since it was already updated in #9802.

[neznaika0]

For the BasicModel, I recently closed PR. We could not agree on the rules of phpDoc - phpstan or simple types.

I stopped correcting the typing.