Upgrade test suite to use generators

[DannyvdSluijs]

This PR will:

• Update all data providers to return Generator objects.
• Remove file headers with a license reference in favour of the LICENSE.md at the root
• Remove class docbocks which where defining unused attributes
• Add declare(strict_types=1); to all test files
• Replace class strings with their resp. ::class constant.
• More updates bringing test files to PHP 7.2 level using rector

[Copilot]

Pull Request Overview

This PR upgrades the test suite to use Generators instead of arrays in data providers while applying additional modernizations across test files. Key changes include:

• Converting test data provider methods to return Generator objects.
• Adding declare(strict_types=1) to all test files.
• Replacing string literals for class references with ::class constants.
• Removing outdated file header comments in favor of a centralized LICENSE.md.

Reviewed Changes

Copilot reviewed 62 out of 62 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tests/ValidatorTest.php	Added strict_types declaration.
tests/Uri/UriRetrieverTest.php	Updated mock creation to use ::class and added strict_types.
tests/Uri/UriResolverTest.php	Added strict_types declaration.
tests/Uri/Retrievers/*	Added strict_types and updated docblocks/license headers.
tests/Constraints/*	Updated data provider methods to return Generator and adjusted JSON decoding to use object mode where needed.
CHANGELOG.md	Updated changelog with a reference to the generator upgrade.