Create parent directory when writing test report

[SquidDev]

This is useful when writing test reports to a child directory, such as $buildDir/reports/tests/gametest.xml instead.

The alternative option here would be to put this call inside a mixin to XmlReportingTestCompletionListener. Creating a subclass felt more elegant, but happy to use a mixin if preferred!

[modmuss50]

I will merge this in alongside the next bunch of changes 👍

[SquidDev]

❤️ Thanks all for reviewing :)

[SquidDev]

Wonderful, thank you so much!