Consolidate logic for collecting js inputs from providers

[alexeagle]

in https://github.com/bazelbuild/rules_nodejs/commit/5ad15960e69906a2c3e2484be9b17d1a77f83221 we observed that this logic is inconsistent. We should have a starlark helper function to iterate through the providers on the deps and collect the exposed JS files that can be input for tools

[github-actions[bot]]

This issue has been automatically marked as stale because it has not had any activity for 90 days. It will be closed if no further activity occurs in two weeks. Collaborators can add a "cleanup" or "need: discussion" label to keep it open indefinitely. Thanks for your contributions to rules_nodejs!

[github-actions[bot]]

This issue was automatically closed because it went two weeks without a reply since it was labeled "Can Close?"

[alexeagle]

Looks like it's too late for this to make 5.0, slipping...