Introduce an `octane` configuration

Recently ember-cli-template introduced an octane configuration which guides users to use new Octane patterns over classic component patterns.

https://github.com/ember-template-lint/ember-template-lint/blob/e10fed889cb6a17fd4d3cffbaa17fbbbbd46e813/lib/config/octane.js

We should introduce the same here for eslint-plugin-ember. I’d be happy to put together a PR introducing the config but we should figure out:

1. What rules should be included in the config
2. What rules are we currently missing?

[rwjblue]

Some possible ideas:

• disallow using actions hash (favoring instead, @action or foo: action(function() {}))
• disallow “classic” classes (preferring native class)

@chancancode / @pzuraq / @Turbo87 / @bmish - Thoughts?

[patocallaghan]

So collating this list from the above comments we have:

• disallow using actions hash (favoring instead, @action or foo: action(function() {}))
• disallow “classic” classes (preferring native class)
• disallow didInsertElement/willDestroyElement() (in favor of modifiers in general)
• only-tagless-components (allows @glimmer/component base class, or tagName: '' if @ember/component)
• disallow @ember/component base class
• enforce component colocation

Two I was thinking of were:

• “no computed properties in native classes”, i.e. always use @tracked
• Similar to the only-tagless-components idea above but instead being no classic components at all

I guess if there is agreement that all of these rules are useful I could create issues for each of them and myself and possibly others could work through the list. Then at the end figure out what needs to go into the actual octane config file.