*: multiple performance improvements
like marking `static const` when it makes sense...
date: change old stupid heap-based method to a structure which should
make copying the thing actually make a copy.
also many performance-based changes, like removing the std::tie
dependency and forward-declaring nlohmann json
*: replace every instance of QString::fromUtf8 to Strings::ToQString.
the main difference is that our function will always convert exactly
what is in the string, while some other times it would only convert
up to the nearest NUL byte