Diagnostics: Change nwnsc for nwn_script_comp

[WilliamDraco]

Recently, the official compiler has been open-sourced as part of the neverwinter.nim project. This compiler matches the toolset capabilities, and updates to the project will be reflected back into the toolset compiler over time where relevant.

Importantly, some new language features are not supported by nwnsc and report errors which are no longer true: For example, Switch-Case statements can now take strings, but nwnsc cannot handle that and reports errors. Swapping to nwn_script_comp would ensure it maintains correct diagnostics/compatibility with any additional features added.

[PhilippeChab]

I've opened a PR to make the change, unfortunately there are two points that need to be addressed before we can go ahead with it. See the PR for the details.