feat: php 8 language level mitigations, add typehints for tests

[Chris53897]

Description of the change

• language level mitigations for php 8. Changes are mostly suggestions from PhpStorm IDE.
• add typehints for /tests/
• small fix in order of arguments in tests (assertEquals)

Type of change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Maintenance
• New release

Checklists

Development

• Lint rules pass locally
• The code changed/added as part of this pull request has been covered with tests
• All tests related to the changed code pass in development

Code review

• This pull request has a descriptive title and information useful to a reviewer. There may be a screenshot or screencast attached
• "Ready for review" label attached to the PR and reviewers assigned
• Issue from task tracker has a link to this pull request
• Changes have been reviewed by at least one other engineer

[danielmorell]

@Chris53897 thank you for the missive amount of work you have put into this! I'm going to need some time to look at this, but I really like what I have seen so far!

[danielmorell]

Thank you this looks really good!