Add possibility to scan for copying pre-built .xctestrun file into test_output directory

[Kukurijek]

Feature Request

It would be nice if scan supported the option to copy .xctestrun file into test_output directory.

Motivation Behind Feature
Running UI tests on a third-party service (e.g. Firebase Testlab) requires a build_products.zip file, which contains a .xctestrun configuration file.

If you want to dynamically insert some settings (e.g. environment variable) when uploading the zip file , you have to unzip the file, change the .xctestrun file (which usually always has a different name) and compress everything again.
Most likely you will do it in a container, which means that you have to install additional libraries unnecessarily.
If you use gcloud, which is quite convenient, you could just pass new .xctestrun file as parameter, so you do not need to zip or unzip anything.

Feature Description
If copy of .xctestrun file (with some default name) is provided in test_output directory, process of delivering UI tests would be much easier.

[rogerluan]

This was implemented here #18057