Upgrade @css-blocks/ember-cli to use the ember addon blueprint.

[amiller-gh]

Because CSS Blocks does not work with full Ember apps quite yet, we could not use the ember addon blueprint to deliver our ember-cli integration and still have our tests pass.

While we work on finishing full Ember integration, we should have a working branch with a fully fledged ember addon at src/packages/@css-blocks/ember-cli.

Once tests pass on this branch (aka: integration is finished and Blocks works in the dummy app) we can merge it in to master.

[Turbo87]

@amiller-gh I'm wondering if we should split glimmer and ember support into seperate packages for now, e.g. @css-blocks/glimmer-css-blocks and @css-blocks/ember-css-blocks. we could still share some of the internals but since the integration will likely be a little different it might make sense to keep complexity low for now by not trying to combine support for both pipelines yet.

[amiller-gh]

PSA: Continued discussion is happening in ✨this PR ✨