Fix strict type errors: miscellaneous fixes in core Kernel tests

Failure seems random

Only hesitation is I wonder if we should wait until everything else is committed before we commit this one, just in case something else slips through before we're ready to turn on strict types. Maybe postponed is better for right now, and we move to RTBC later?

To be explicit: I reviewed the MR and agree this is RTBC, I'm only wondering on the ordering/timing.

Had the same thoughts, and agree. Postponing.

Need to migrate changes mentioned in [#3404508:11] to this issue.

This is unblocked now. The MR at https://git.drupalcode.org/project/drupal/-/merge_requests/6826 demonstrates that adding these fixes and declaring strict types everywhere results in a green pipeline. So if we get this in we can update 📌 [PP-2] Add declare(strict_types=1) to all Kernel tests Postponed and get that in also.

Looking at the MR in #9 see the change here doesn't break anything and allows for adding strict type.

Committed f60bcea and pushed to 11.x. Thanks!
Committed 8331ba7 and pushed to 10.3.x. Thanks!
Committed cb25ccb and pushed to 10.2.x. Thanks!

Backported what I could to 10.2.x to keep the tests aligned

Automatically closed - issue fixed for 2 weeks with no activity.