[1.44] Cherry pick various upstream fixes

Lots of fixes from stable releases cherry-picked to 1.44 branch.

I've adapted the CI job, however there's a failure (and just one) in fedora 32 (not in ubuntu 20.04), but I'm not sure why. Given that it's also happening with 1.44.7 and previous stable releases of the 1.44 branch (the ones that compile, at lest).

Thus for sure not related to these changes (whose tests pass all correctly in fact).

+++ /tmp/.ARD320	2021-05-05 16:19:35.271641398 +0000
@@ -16,8 +16,8 @@
 i=1, index=0, paragraph-start=1, dir=ltr 'This paragraph should ac­tual­'
 i=2, index=32, paragraph-start=0, dir=ltr 'ly have multiple lines, unlike '
 i=3, index=63, paragraph-start=0, dir=ltr 'all the other wannabe äöü pa­'
-i=4, index=96, paragraph-start=0, dir=ltr 'ra­graph tests in this ugh '
-i=5, index=124, paragraph-start=0, dir=ltr 'test-case. Grow some lines!
+i=4, index=96, paragraph-start=0, dir=ltr 'ra­graph tests in this ugh test-'
+i=5, index=129, paragraph-start=0, dir=ltr 'case. Grow some lines!
 '
 i=6, index=152, paragraph-start=1, dir=ltr ''
 
@@ -29,8 +29,8 @@
 i=4, index=63, no run, line end
 i=5, index=63, chars=29, level=0, gravity=south, flags=4, font=OMITTED, script=latin, language=en-us, 'all the other wannabe äöü pa­'
 i=6, index=96, no run, line end
-i=7, index=96, chars=27, level=0, gravity=south, flags=0, font=OMITTED, script=latin, language=en-us, 'ra­graph tests in this ugh '
-i=8, index=124, no run, line end
-i=9, index=124, chars=27, level=0, gravity=south, flags=0, font=OMITTED, script=latin, language=en-us, 'test-case. Grow some lines!'
+i=7, index=96, chars=32, level=0, gravity=south, flags=0, font=OMITTED, script=latin, language=en-us, 'ra­graph tests in this ugh test-'
+i=8, index=129, no run, line end
+i=9, index=129, chars=22, level=0, gravity=south, flags=0, font=OMITTED, script=latin, language=en-us, 'case. Grow some lines!'
 i=10, index=151, no run, line end
 i=11, index=152, no run, line end
not ok 5 /layout/valid-4.markup
Bail out!