Automatically use property count in PropertyListHelper

[KoBeWi]

Now that PropertyListHelper has a getter for array size, it can be used instead of manually passing the count when getting property list.
Conflicts with #92282, this should be merged first.

[akien-mga]

There's a segfault on CI, but no stacktrace. I'd suspect the added memdelete. Maybe it's only created conditionally?

[KoBeWi]

There is a DEV_ASSERT for existence of array_length_getter, so it should always exist.

[KoBeWi]

For some reason the additional checks have helped, but they shouldn't be necessary. It would be nice to know where the code crashed.

[KoBeWi]

I think I know when can this happen. Constructors for static helpers can run without the class being instantiated, so the object is created and destroyed afterwards, but never initialized.

EDIT:
Improved the code.

[akien-mga]

Thanks!