Fix errors ignored in phpstan-baseline.neon

We can temporarily/locally lower the phpstan level to 0, generate the baseline with that level, remove those errors, bump it back to 6, then regenerate the baseline again - that would give us an MR per phpstan level then doing the most glaring issues first. Then if we need to split things out into smaller issues from there can do that too.

Around 200 remaining 🤯

Down to 17, worth checking some of those eventually but phpstan also has issues plus fixing some would be needless struggle only.
Merge train running.