Raise min version to PHP 7.3, check compatibility PHP 8.3.

[terabytesoftw]

Q	A
Is bugfix?	❌
New feature?	✔️
Breaks BC?	❌

[what-the-diff]

PR Summary

• Updated GitHub Actions in build.yml
  Updated to the latest versions of GitHub Actions in our workflow to ensure smooth, efficient and secure operation.
• Upgraded PHPUnit Package
  The package phpunit/phpunit used for testing has been upgraded to the latest version (^9.6) improving the accuracy and reliability of our unit tests.
• Adjusted Exception Expectations in Tests
  Tests in AccordionTest.php have been updated to expect an InvalidConfigException, ensuring our testing setup aligns with the expected software behaviors.
• Code Formatting and Setup Method Updates in Several Test Files
  Minor code formatting adjustments and an update to the setUp method in several test files for maintaining a consistent style and performance.
• Updated Test Output Expectations
  Tests in ButtonDropdownTest.php, and CarouselTest.php, were updated to expect specific output, confirming our components deliver the expected HTML output.
• Method and Class Renames in Test Files
  To increase readability and clarity, several methods and a test class have been renamed in ToggleButtonGroupTest.php.
• Removed Redundant File and Checks
  The compatibility.php file and certain class checks in mentioned file, have been removed from the tests folder, helping to streamline our codebase.

Note: This PR mostly includes maintenance updates improving the efficiency, reliability, and readability of our test suite and build process.

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[mtangoo]

Shouldn't this go up to at least 7.4 for the version before raising to 8.1?