All of these can be migrated into the cpp file, since they're only used
there.
Greatly reduces the amount of work the preprocessor has to do in files
that include this one.
All of these entries make use of captureless lambdas, so there's no need
to make use of std::function. We can just use a regular function
pointer, which allows making all of the file-static entries within
IScriptObject constexpr. Eliminating all of their runtime static
constructors.
