Refactor of `Zend\Db\ResultSet` for 3.0.0

[arueckauer]

This PR provides changes described in #364

I have two questions from refactoring.

1. Return type hints for implementations of \Iterator::current() is incomplete due to inconsistent usage. Right now, type hints are only documented in method comment. Either leave it or a change is required to match return types.

• Iterator::current() documents a mixed (any) type
• AbstractResultSet::current() documents array|null
• ResultSet::current() documents array|ArrayObject|null
• HydratingResultSet::current() documents null|array|bool

2. ExtractionInterface::extract() expects parameter be of type object. From my understanding HydratingResultSet::toArray() could give provide any of null|array|bool. Not sure if I misunderstand it or if that needs some attention.

[weierophinney]

This repository has been closed and moved to laminas/laminas-db; a new issue has been opened at https://github.com/laminas/laminas-db/issues/12.

[weierophinney]

This repository has been moved to laminas/laminas-db. If you feel that this patch is still relevant, please re-open against that repository, and reference this issue. To re-open, we suggest the following workflow:

• Squash all commits in your branch (git rebase -i origin/{branch})
• Make a note of all changed files (`git diff --name-only origin/{branch}...HEAD
• Run the laminas/laminas-migration tool on the code.
• Clone laminas/laminas-db to another directory.
• Copy the files from the second bullet point to the clone of laminas/laminas-db.
• In your clone of laminas/laminas-db, commit the files, push to your fork, and open the new PR. We will be providing tooling via laminas/laminas-migration soon to help automate the process.