bug#37689: Fringe pixmaps, widgets, etc. look ridiculously tiny in hidpi screen

[Carlos Pita <carlosjosepita@gmail.com>]

> Maybe I'm confused: I thought we were talking about fringe bitmaps.
> But you seem to be talking about a more general issue.  I'm not sure

Yes, remember how all this started:

> make an inventory of all the things that should be fixed towards hidpi

Above I've been mostly talking about two things: i. fringe bitmaps and
ii. widgets (checkbox-like stuff). My main interest is in (i) since
I'm ok with text-only widgets but there is no replacement for fringe
bitmaps. Anyway, I would like to fix both things at the same time.
Moreover, there are other problems, which might be addressed by the
same changes or not, take for example tetris, which looks laughably
small in my screen.

So I could go and  change get_fringe_bitmap_data and hopefully fix the
fringe issue but:

i. This won't fix any other hidpi issues.
ii. This might introduce regressions in backends that I'm unable to
test (windows, macos) because they might be doing the scaling
themselves.

Therefore I believe a more nuanced understanding of how emacs is
approaching the matter, if there is any strategy at all, is in order.