Adapt to latest libunicode, making use of new grapheme_line_segmenter API #6699

Job	Run time
Check C++ style	34s
Check CI scripts	3s
Check PR-TODOs	2s
Archlinux ${{ matrix.arch }}	0s
Check links	9s
Check clang-tidy	1m 45s
Check editorconfig	8s
Fedora 39 linux/amd64 x86_64	2m 19s
FreeBSD 13	0s
macOS	3m 59s
Windows	3m 24s
Build notcurses (20.04)	3m 39s
Packaging for Ubuntu 20.04	3m 19s
Build notcurses (22.04)	3m 32s
Packaging for AppImage	3m 30s
Packaging for Ubuntu 22.04	3m 56s
Ubuntu Linux 22.04 (GCC 10, C++20, Qt6)	3m 14s
Ubuntu Linux 22.04 (Clang 15, C++20, Qt6)	3m 17s
Check Release	0s
GUI: Quick Shell Exit	0s
Check packages for Ubuntu	0s
GUI: notcurses-demo ${{ matrix.name }}	0s
tests matrix	1s
Create Github release	0s
Run bench-headless	0s
Run tests via valgrind	0s
Ubuntu Linux 22.04 post-check	2s
	36m 53s

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