[TASK] Improve type annotations for (Lazy)ObjectStorage

Make proper use of generics and align the API of our classes
with that of the implemented interfaces `Iterator` and
`ArrayAccess`.

This helps extension developers use static analysis for their
extensions.

This is a pre-patch to introducing native types for the two
classes.

Resolves: #102958
Related: #102956
Releases: main, 12.4
Change-Id: I19f850264040246ef140c6958d20473ef4c9be28
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/82620


Tested-by: core-ci <typo3@b13.com>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>