Return (and potentially initialize) the hierarchy singleton
Logger themselves have little knowledge about their hierarchy.
Everything is handled by a HierarchyT!(Logger) instance, which is
stored as a singleton in this struct, and for which convenient
functions are provided.
This function returns said singleton, and initialize it on first call.
Return (and potentially initialize) the hierarchy singleton
Logger themselves have little knowledge about their hierarchy. Everything is handled by a HierarchyT!(Logger) instance, which is stored as a singleton in this struct, and for which convenient functions are provided. This function returns said singleton, and initialize it on first call.