Add dts bundling

This adds a "small" d.ts bundler script. This script is very basic,
using Node printing to produce its output. Generally speaking, this is
inadvisable as it completely disregards name shadowing, globals, etc.
However, in our case, we don't care about the globals, and we can opt to
restructure our codebase in order to avoid conflict, which we largely
had to do anyway when we were namespaces and everything was in scope.

src/compiler/commandLineParser.ts

@@ -2073,7 +2073,7 @@ function getTsconfigRootOptionsMap() {
 }
 
 /** @internal */
-interface JsonConversionNotifier {
+export interface JsonConversionNotifier {
     /**
      * Notifies parent option object is being set with the optionKey and a valid optionValue
      * Currently it notifies only if there is element with type object (parentOption) and