Extend pipeline for newer versions php

[DannyvdSluijs]

This PR updates the pipeline to include PHP >= 8.0 and no longer include PHP <= 7.1. In addition the PR contains the following changes to have green results.

• Update to PHPUnit 8.5 to resolve invocations of deprecated/removed method each(), see https://www.php.net/manual/en/function.each.php. Which resulted in:
  • Add void return types to ::setup() methods
  • Explicitly include phpspec/prophecy
  • Replace ::setExpectedException() and @ExpectedException for ::expectException
  • Replace ::assertInternalType() with assertIs*() methods
  • Replace ::getMock() with ::createMock()
• Improve test assertions in case of warning or error during test run.
• Port Fix ObjectIterator for PHP8 #682 to fix deprecations from ObjectIterator
• Port [PHP 8.4] Fixes for implicit nullability deprecation #717 to fix implicit nullable deprecations
• Update icecave/parity to ^3,0 to resolve invocations of deprecated/removed method each()
• Correct styles reported by GHA workflow

[Seldaek]

Looking good !