Add support for import with node: (#1405)

This PR adds support for pkg to identify any built-in/core module that's being imported using the `node:` protocol. 

Fixes: #1309, #1363

Author: mallardduck

lib/walker.ts

@@ -846,7 +846,10 @@ class Walker {
   ) {
     for (const derivative of derivatives) {
       if (natives[derivative.alias]) continue;
-
+      if (derivative.alias.startsWith('node:')) {
+        if (natives[derivative.alias.substr(5)]) continue;
+      }
+      
       switch (derivative.aliasType) {
         case ALIAS_AS_RELATIVE:
           await this.stepDerivatives_ALIAS_AS_RELATIVE(