[Feature] Swappable renderer

Based on how much struggle I've been having with the VM latetly:
- https://github.com/glimmerjs/glimmer-vm/pull/1563
- https://github.com/glimmerjs/glimmer-vm/pull/1547
- https://github.com/emberjs/ember.js/issues/20644
- https://github.com/emberjs/ember.js/issues/20643
- https://github.com/emberjs/ember.js/issues/20642
- https://github.com/emberjs/ember.js/issues/20631
- https://github.com/emberjs/ember.js/issues/20610
- https://github.com/emberjs/ember.js/issues/20535
- https://github.com/emberjs/ember.js/issues/20628

**_And_** with the lack of ability for folks to iterate on implementing language improvements: https://github.com/emberjs/rfcs/issues/816 (not due to lack of trying, but due to how the VM is hard to work with / maybe has a lot of baggage)

**_And_** with the amount of progressing happening on an alternate renderer:

- compat todos are done: https://github.com/lifeart/glimmer-next/issues/10 (we'll see tho if it works with ember-modifier, ember-resources, and bigger projects)
- faster reactivity technique: https://github.com/lifeart/glimmer-next/issues/41 (Update-only VM)
- looks like this is a list of remaining stuff: https://github.com/lifeart/glimmer-next/issues/3

glimmer-next compared with svelte and ember

https://krausest.github.io/js-framework-benchmark/2024/table_chrome_121.0.6167.85.html#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



**_And_** with the desire to use Starbeam in the future, tho no one is really working on that as I write this

**_And_** with how we don't score whell in https://github.com/krausest/js-framework-benchmark (like it or not, this is how we are judged, so we must play the game)

**_And_** since we kinda need to migrate away from a pure-JSON representation of the complied templates so that we can explore more expressive syntax (something glimmer-next is already prepared to enable)

**_And_** with the ovelwhelming effort it feels like it would take to merge the 3 repos:
- this one: https://github.com/emberjs/ember.js
- glimmer-vm: https://github.com/glimmerjs/glimmer-vm
- glimmer.js: https://github.com/glimmerjs/glimmer.js
(which honestly needs to happen anyway)

I've been wondering if we can work out a minimal public/intimate API for completely swapping out glimmer-vm / runtime such that folks can better experiment with improvements to ember.

As a quickly, barely thought out psuedo API, it could look like this, to support what we have today
```js
import { registerRenderer } from '@ember/renderer';
// idk if these are real, but not the point
import { render } from '@glimmer/vm';
import { runtime } from '@glimmer/runtime';

registerRenderer({ render, runtime });
```

which could allow for someone to easily choose to use `glimmer-next` without forking ember-source.
```js
import { registerRenderer } from '@ember/renderer';
// idk if these are real, but not the point
import { render, runtime } from 'glimmer-next';

registerRenderer({ render, runtime });
```

Or could allow someone to work on developing a _native_ renderer for iOS and Android.

```js
import { registerRenderer } from '@ember/renderer';
// idk if these are real, but not the point
import { render, runtime } from 'glimmer-android';

registerRenderer({ render, runtime });
```

------------

One may consider that we have a lot to do, and we don't have enough steam to work on anything like this (like a native renderer).

I think we have people who currently aren't contributing as much, but _would_ if they were able to, so we could enhance our parallel efforts -- widen the pipe, so to speak

------------

Note as well, this issue could also be a call-for-help to have someone dedicate a bunch of time to improve the existing glimmer-vm.