Interop Gen: Support `never` type

[nikeokoronkwo]

This PR is for adding support for generating equivalent typing for JS's never type.

never in JS is similar to the Dart Never type. Some cases for the never type include:

• throwing exceptions (in the form of JS's Error type)
• undefined & <other>

This PR should convert such types to JSAny (since void/JSVoid is not a JS interop-able), and ensure such values are not used by annotating with @doNotStore.