remove condition preventing core moduleIds from resolver

[iambumblehead]

Per the resolver spec, the resolver should handle builtin module names

PACKAGE_RESOLVE(packageSpecifier, parentURL)
...
3. If packageSpecifier is a Node.js builtin module name, then
. 1. Return the string "node:" concatenated with packageSpecifier.

This PR removes a condition that prevented the resolver from being called with builtin moduleIds and

• slightly simplifies esmock, esmock calls the resolver with any moduleId
• anticipates that the resolver is spec compliant and handles builtin moduleIds

[iambumblehead]

its published :) esmock is improved

[koshic]

Yeah, thx again! ) Now my turn - to tweak pnp resolver a bit and provide wiki example.