track export * identifiers to detect collisions.

[jdalton]

To detect collisions of say

let a = 3

export { a}
export * from "./abc.js" // where abc.js also exports "a"

You'll need to track identifier origins.
This can be done more easily when you implement the load order of waiting on child modules to load before triggering the Entry#loaded() since that will remove the need of capturing multiple module owners so you can associate an identifier with 1 owner module.