[Beta Bug] Intermixing attrs and non-attrs on closure actions become mutable cells

[chadhietala]

Repro:
https://ember-twiddle.com/1be97289c3f77efac3ac851a22626595?openFiles=templates.application.hbs%2Ctemplates.components.my-middleman.hbs

I'm not sure how we did this before in HTMLBars, but when you go from foo=(action 'foo') and pass it to child as fooAction and that child tries to call it as this.attrs.fooAction, it will be a MutableCell and not the actual closure action.

[rwjblue]

@chadhietala - I believe this issue is basically what I have submitted a failing test PR in #13996 for. Can you confirm?

[chadhietala]

Yes

[rwjblue]

Fixed by #13996