Task/update phpunit 9.6

[tijmenbruggeman]

Updated PHPUnit to 9.6.22

Description
There are newer version of PHPUnit but 9.6.22 we already had a lot of deprecations in 9 so will update step by step.

• Return types for compatibility with framework
• define plugin_basename because dirname does not accept null
• Replace PHPUnit_Framework_TestCase with \PHPUnit\Framework\TestCase
• Replace setExpectedException with expectException