refactor: Update test case to current (PHP) standards

[DannyvdSluijs]

This PR improves the test cases classes and addresses some small fixes of issues which exposed themselves.

[Copilot]

Pull Request Overview

This PR refactors the test cases to update them to current PHP standards and improve type safety and code clarity. Key changes include:

• Replacing instance property access with class constants for test paths.
• Adding strict type hints and updated doc annotations for better maintainability.
• Removing a redundant test case and updating JSON decoding across tests.

Reviewed Changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tests/Drafts/Draft4Test.php	Removed the $schemaSpec property and updated test properties.
tests/Drafts/Draft3Test.php	Updated file path resolution to use a class constant rather than an instance property.
tests/Drafts/BaseDraftTestCase.php	Replaced property with a constant and updated type annotations.
tests/Constraints/VeryBaseTestCase.php	Refactored schema retrieval methods with improved type hints and file handling.
tests/Constraints/ConstTest.php	Updated JSON test schema to use "object" instead of "any".
tests/Constraints/BaseTestCase.php	Updated type hints and json_decode calls for better consistency.
tests/Constraints/ArraysTest.php	Removed a test case related to array items validation.
CHANGELOG.md	Updated changelog reflecting these substantive test improvements.

Comments suppressed due to low confidence (2)

tests/Drafts/Draft4Test.php:16

• The removal of the $schemaSpec property in Draft4Test may break tests that rely on it (for instance, in BaseTestCase where it is used to set the '$schema' property). Consider reintroducing $schemaSpec or refactoring the tests to remove the dependency on it.

protected $schemaSpec = 'http://json-schema.org/draft-04/schema#';

tests/Constraints/ArraysTest.php:272

• The removal of the 'items: true passes validation' test case may reduce coverage for array item validations; please confirm that its removal was intentional and that all necessary scenarios remain adequately tested.

'items: true passes validation' => [ ... ]