Tree passed to preprocessors for app and addon is not scoped with moduleName

[wondersloth]

Replicated the issue here:
https://github.com/wondersloth/demo-embroider-preprocessors-bug

When a preprocessor is run on an app or addon, the tree isn't scoped with the moduleName.

This creates backcompat issues with addons like ember-css-modules that uses the file path to generate hash for some values.

• css file hash doesn't use correct path when generating-scoped-name in embroider app build, when consuming an addon using ecm salsify/ember-css-modules#278
• Fixed composes issue for embroider + v1 addon salsify/ember-css-modules#279

[ef4]

Closed in #1205.