Add deprecation for the Ember Global

[patocallaghan]

Towards RFC 706

Adds a deprecation for the Ember Global

{
  id: 'ember-global',
  until: '4.0.0',
  url: 'https://deprecations.emberjs.com/v3.x/#toc_ember-global',
  for: 'ember-source',
  since: {
    enabled: '3.27.0',
  },
}

Can this PR be merged as-is or do we need to wait for a new release of ember-cli-babel with emberjs/ember-cli-babel#382?

[patocallaghan]

Ah I have some failing tests I need to resolve 😬

[pzuraq]

@patocallaghan I'm actually detangling some things to do with this now, turns out that the Globals resolver/namespaces are being accessed when logging class names 😬 I'm going to see if I can't remove that code in a separate PR that you can rebase on top of

[patocallaghan]

@pzuraq ah thanks. Yeah it seems to be happening in the internals here in the namespace_search.ts class.

[patocallaghan]

Rebased to pick up the changes from #19467