icingaweb2_dev: add Package[php-phpunit-PHPUnit]

refs #6842
icingaweb2_dev: enable `test' module

refs #6842
icingaweb2_dev: add Package[icinga-gui]

refs #6842
Merge branch 'feature/deduplicate-puppet-code-6842' into feature/Test-deduplicated-Puppet-code-7321