✨ New exhaustive check feature

[ShepherdSoasis]

This Pull Request adds a new exhaustiveness check feature. The tests were updated, and some general fixes were applied in line with what @ThePhD asked for earlier.

• It adds the sol:::exhaustive<T> and sol::exhaustive_until<T, N> types & related feature. This forces the type checker to dig into container-like types. It checks if the entire table (or up to N elements in a table) pass the type check.
• This allows someone to differentiate e.g. a std::vector<TypeA> from a std::list<TypeB> properly when sourced from a Lua Table.
• The assert macro name was changed to all UPPERCASE, as it hygenic, and the name for the message assert was changed.
• FetchContent is used to grab the data where possible in the LuaVanilla build. This may need additional tweaking to ensure it works in all environments.
• The "run_time" tests were blocked off as they are still broken and unable to work. They should be kept blocked off until they are more appropriately audited and moved to separate sub-projects, similar to container_exhaustive and others.

[ShepherdSoasis]

We fixed some of the compilation errors on this PR (finally). The tests still fail due to some issues with the automatic lua pulling and building system; we feel this should be fixed soon. Nevertheless,

ok to merge?

[ThePhD]

Yes, sorry; thanks for doing this. This will help immensely with allowing overriding in this specific case, and cleaning up the assert macro was very helpful. There's more to do in this direction but I think this helps enough. I need to clean up the tests and similar so that we have a proper working point, but there is.... SO much to fix in this repository....