Add action to expand _service file

[bwachter]

The runservices script from build can be used to run all services in a _service file with minimal setup. Some services don't make sense in a gh action workflow, though, so unclear yet if it'd be better to do a custom entry point for that which filters services to run.

Services have different requirements, for the ones we care about should be typically solved by setting a few variables that'd exist in a build root manually.

This action would run before kiwi-build actions to expand obs style tags before building the image.