* Split unit test over multiple jobs in GitHub Actions, lowering the total run time
* rename FileManipulationTest to FileManipulationTestCase so it does not run as a standalone Test
* Bumped phpspec/prophecy version to prevent 7.4 deprecations
* Fix DOMDocument::$config type
This property was documented as containing DOMConfiguration object, but
in fact always returned `null` (see [php source](ee80567a83/ext/dom/document.c (L542))).
DOMConfiguration class is removed in PHP 8.
* Dropped unused use
* Allow to set PHP 8.0 as current version
* Fix CallMap issues for PHP 8.0
- Use both major and minor version to load deltas
- Don't load non-existent deltas
- Stop at lowest possible delta