Move sendCoverage to be added by the host in QUnit.done

[thoov]

After testing out the beta inside of a large internal embroider app these changes were needed:

1. Moving sendCoverage to be invoked by the end user (e.g. in QUnit.done)
2. Adding a default namespace so that embroider apps without symlinks work correctly (if you symlink an addon into an embroider app the workspaceDir will look like: /tmp/embroider/hash/app-namespace/app.js and /tmp/embroider/hash/linked-project-namespace/foo.js whereas without the link it looks like: /tmp/embroider/hash/app.js)
3. Adding node_module exclusion to the default excludes as just a perf boost under embroider.

---

The setup for consumers changes in the following ways:

• Remove the <script> for /coverage.js in tests/index.html
• Update tests/test-helper.js to something like:

import Qunit from 'qunit';
import { forceModulesToBeLoaded, sendCoverage } from 'ember-cli-code-coverage/test-support';

QUnit.done(async function() {
  forceModulesToBeLoaded();
  await sendCoverage();
});

[rwjblue]

This seems vaguely odd. I wonder if we should consider always using a consistent structure over on the Embroider side.

[thoov]

👍🏻