Remove Scripty

As discussed in #48 (closed), specifically here, it is desirable to remove the dependency on Scripty. To summarize the rational, the code being generated is stable enough that it doesn't need to be regenerated on every build.

The plan of action:

1. Remove Scripty dependency.
2. Remove Scripty 'csx' generation files.
   • Note, keep the code. See below.
3. Remove any other 'csx' infrastructure code.
   • Note, keep the code. See #55.
4. Keep the already generated 'cs' files.

If any the code is complex enough to need generation, this should be done with dedicated console apps that generate the code text that can be manually added to the project files. For example, CommonCore.SourceGeneration.NumericExtensions would generate the NumericExtensions.cs file, and maybe also the Thrower.NumericExtensions.cs file, locally and then those files would be manually copied to the CommonCore project itself.

This would remove a dependency, reduced unneeded regeneration of stable code, retain the ability to regenerate the code when needed, and overall remove unnecessary technical debt from the core library.