circular import between @ember/object/index and @ember/object/observable

[patricklx]

🐞 Describe the Bug

there is a circular import between
'@ember/object/index';
and
'@ember/object/observable';
and
@ember/array/index.

those files are actually also importing from @ember/-internals/metal, so they could use that directly to access get, set

https://github.com/emberjs/ember.js/blob/main/packages/%40ember/object/observable.ts#L14
https://github.com/emberjs/ember.js/blob/main/packages/%40ember/object/index.ts#L13

this causes rollup to sometimes build it wrong and have runtime errors later. (testing with vite+dep optimizer)

[kategengler]

cc @ef4

[ef4]

Fixed in #20734