(3.x) fix 280260: added an option to set the default font for all text types

[SKefalidis]

Resolves: 3.x version of #5816

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[SKefalidis]

Added button:

[Tantacrul]

I think it's cool we've addressed this problem. I do think we need a slightly more blunt and discoverable option. I also dislike putting this here. I have a few suggestions for an alteration or two. Really glad the functionality has been built though!

[shoogle]

@Tantacrul, how does the above compare to my suggestion here? Basically there would only be a single font dropdown and no button. The dropdown would initially show "Edwin", and if it was subsequently changed to "Noto Sans Arabic UI" then all text styles that were previously using Edwin would be updated to the new font.

[vpereverzev]

It's a feature-freeze stage for 3.6 now, so I'll close this PR, because it's a kind of feature that should be implemented carefully.
I suggest to focus on a version for master and consider @Tantacrul UX suggestions.

[Jojo-Schmitz]

I'll try to merge it into #9000