intl.accept_languages gets into a stuck modifed state

grrr ... so I was testing some locale changes for TB health checks: namely that the languages are exactly what they should be: i.e supported, correct case, correct order. And that the locale matches (language !== locale is not good enough, e.g. it-IT language uses it locale), also correct case. I am excluding android for now as I believe that we don;t have parity and/or there is something going on with case (e.g. en-us, or even what is used, e.g. en vs en-US .. blah blah)

So I was messing around adding languages. Whilst in en-US, I added French, then Danish

and when I added Danish, I got the apply and restart, so I did - and this is what happened

so my locale matches Danish, but my languages were never set correctly. The languages in the UI are as per the first pic

So now I decide to go back to en-US and replicate my steps for you, so I choose to change to english and apply and restart and this is what I get - NOTE I cannot remove Dansk or Francais ... and after some more fiddling, can't remove Espanol, Cestina

So not only does the UI become borked, but looking at the first image, we fubar the fingerprint. I think when we apply a language change we need to properly reset the UI and navigator properties edit AND locale

cc @pierov