[cleanup]: class based fastboot service

[snewcomer]

This PR just seeks to cleanup some code and deprecations

close #815

[ef4]

👍

I'm not sure what the support matrix is between fastboot and ember-cli-fastboot but this change means fastboot will be dropping support for ember-cli-fastboot prior to #841.

[snewcomer]

Actually we could go about it another way. When I originally did the PR, this was one of the test cases. We need to add a setter for it to not raise a deprecation.

https://github.com/emberjs/ember.js/pull/19358/files#diff-2600f49bdcd760f57af70712f38930aca2c85c30752165032d9998359ed9109dR265-R295

[snewcomer]

@ef4 I've changed the scope of this PR and opened a new PR with the actual fix that works - #857.

change means fastboot will be dropping support for ember-cli-fastboot

However, all injections do need to be dropped for 4.0. From your point of view, what is the concern if we aren't injecting directly onto the fast boot service from ember-cli-fastboot?

Nvmd I see it. The fastboot package's files aren't directly available in ember-cli-fastboot anymore.