Add active-model-adapter to partner tests

[igorT]

Especially as we will be refactoring the adapter/serializer area soon

[dcyriller]

@igorT I've started to look into this. I'm interested - being a user of active-model-adapter.

To add active-model-adapter to partner tests, I will open a PR to remove bower usage there.

But I also have a question... Is it ok to also not publish anymore the package on rubygems? Indeed, it looks that active-model-adapter is published on rubygems under the name active-model-adapter-source. It would be used by the ember-rails project to add frontend capabilities to a rails app. None of the projects are deprectated, but I assume that consumming an ember addon through the ruby gem is not recommended anymore - and difficult to support. After that, we'd release a 3.x version. If any patch needs to be applied on active-model-adapter-source, it would be done on a 2.x branch.

[dcyriller]

I see a PR has already been started to drop bower 🎉 adopted-ember-addons/active-model-adapter#121

[runspired]

closing in favor of #7529 7529