Throw on `ConfigurationFactory::getConfiguration` failures

[vy]

Existing ConfigurationFactory::getConfiguration methods return null on failure. As discussed earlier (see this dev@ thread, or #3839), we should throw on failures instead. An example of this behaviour is implemented in #3921 for the newly added getConfiguration(LoggerContext,String,List<URI>) overload. This issue proposes change ConfigurationFactory::getConfiguration methods to throw on failures.