remove dependency on ember-cli-head

[MelSumner]

TODO: Change ember-page-title to remove the ember-cli-head requirement (for both SSR and in browser)
Teams will have to add the ember-cli-head addon if they want the functionality from both.

This will unblock the related RFC

We'll need to create a new release and do a major version bump.

Notes:
After this is finished, update RFC 645 to add both ember-page-title and ember-cli-head as dev dependencies of apps.

[knownasilya]

Any tips on how to approach this? Manually update the title?

[buschtoens]

What about fastboot? 🤔

[MelSumner]

@knownasilya that's a good question- I'm going to try to look at it today, but maybe @rwjblue has some advice if he can get to it before me.

[rwjblue]

We don't need ember-cli-head in order to support FastBoot. The scenarios that we need to care about are:

• client side render (no rehydration)
• client side render (rehydrating prior)
• server side render

Both of the client side renders can be accommodated by manipulating document.title directly.

The server side render can be manipulated by setting .title on the internal/private SimpleDOM document. For example, like this:

let document = owner.lookup('service:-document');
let titleEl = document.createElement('title');
let titleContents = document.createTextNode('whatever the title contents should be');
titleEl.appendChild(titleContents);
document.head.appendChild(titleEl);

[rwjblue]

For more context, the service:-document thing is passed through here, and it is basically either going to be the normal global document instance or the FastBoot created SimpleDOM.Document (see here for some inline docs and where that BootOptions is built in FastBoot).

[raido]

Just letting know that I am experimenting implementing this. Having some Fastboot issues for few test cases. If I cannot resolve them I'll open draft PR for help.

[raido]

Here's a draft PR - #168