Offline QA: specific configuration of the QA task

The commit introduces the possibility of the specific QA task configuration withing the QA-config yaml file.
In the yaml-file, the configuration should be defined under qa/<task name>/specific node. On the task side
the configuration is represented with a plain structure (Config), which can be defined using the function
std::optional<Config> CbmQaTask::ReadSpecificConfig<Config>() in the task initialization function (for
expample see the CbmCaInputQaBase class implementation).

The specific configuration feature is optional and can rely on the default-initialized Config structure, so the "specific" branch
of the QA-configuration file is not mandatory.