[kprocessrunner] Clean up maybeAliasedName
maybeAliasedName does two things:
- resolving the potential alias for m_service
- Fill in a given pattern with the result and a UUID
Mixing those two things in a single function is dangerous.
For requestXdgActvationToken we want to resolve the alias, but not do any of the pattern/UUID stuff that is only for the system runners.
Shuffle things around to make it more clear.
Also make sure that m_service is set before resolveServiceAlias is called