Rename module identifier by wrapping program.body with IIFE.

[benjamn]

Before this change, in order to obtain a reliable reference to the original module object, the Reify compiler would inject a variable declaration at the beginning of the generated code that bound some other (uniquely named) variable to the module object, and then that unique variable was used in all the other Reify-generated expressions, such as module1.export(...) and module1.link(...).

The trouble with this strategy was that the injected variable declaration could still collide with other declarations in the module scope that involve the module identifer.

A better way to solve that problem is to introduce another scope by wrapping the module code in an immediately invoked function expression. The original module object can be passed as an argument to that function, and the corresponding parameter can be uniquely named:

(function (module1) {
  module1.export({ name: () => name });
  module1.link("some-module", ...);
  // ...
}).call(this, module);

However, this wrapping should happen as late as possible, in some cases after multiple invocations of the Reify compiler, so the wrapping should not be the responsibility of the Reify compiler itself. Instead, the compiler should just use whatever options.moduleAlias is passed in, and not second-guess it or attempt to inject any variable bindings.

In this PR, the Babel plugin (reify/plugins/babel) becomes responsible for the IIFE wrapping shown above, while also gaining the ability to transform the AST twice: upon entering and upon exiting the Program AST node. This double transformation is necessary to transform both import and export declarations found in the source code, and those that were injected later by other transforms, such as @babel/plugin-transform-runtime.

[benjamn]

As you can see from these updated tests, many of the const module1 = module renamings were unnecessary false positives before this change.