Fix namespace tracing - #2408

I do not like adding the module as a parameter here as this breaks the encapsulation created by the AstContext. As the AstContext already has a traceExport function, maybe this can be avoided by adding a new method to the NamespaceVariable that does a trace inside this variable's module using its AstContext's traceExport function? This should cover the only usage of .module in Chunk while keeping encapsulation of the AST from the module.

I disagree about the encapsulation point, as I think it should be possible to trace up the parent hierarchy for any object. Plain data structures will always be a better abstraction than function closures. Yes we're exposing a class, but we're really after the "data representing the module semantically".

The additional point here is that there are two traceExport functions - one for Module which does direct tracing, and one for Chunk which does chunk to chunk tracing. I did initially spend many hours trying to make these share the same routine but in the end it was much easier this way around.

I see. Yes, switching to plain data structures would definitely be a great improvement as it would also allow nice serializations etc. As you have guessed, my issue is with having the "rich" data structure of the module attached to the namespace variable while we go to great lengths to encapsulate the Module methods from the AST in the context.
Then at least we should add a comment to the module field that it is only meant to be used for tracing exports in the Chunk to avoid people in the future actually accessing properties on it to make other things "work" instead of thinking about the architecture.

Just added a clarifying comment