Implement `[[ fragment literals ]]` #4238

Job	Run time
macos-static	2m 1s
windows (32, windows-2019)	5m 9s
windows-mingw-build (32)	1m 11s
windows-mingw-build (64)	55s
windows (32, windows-2022)	5m 32s
cygwin (32)	5m 15s
freebsd	5m 14s
windows (64, windows-2019)	5m 31s
cygwin (64)	4m 58s
windows (64, windows-2022)	5m 41s
unix (ubuntu-20.04, g++, make)	5m 56s
unix (ubuntu-20.04, g++, cmake)	5m 51s
unix (ubuntu-20.04, clang++, make)	6m 21s
unix (ubuntu-20.04, clang++, cmake)	6m 42s
unix (ubuntu-22.04, g++, make)	6m 48s
unix (ubuntu-22.04, g++, cmake)	6m 35s
unix (ubuntu-22.04, clang++, make)	4m 35s
unix (ubuntu-22.04, clang++, cmake)	4m 38s
unix (macos-14, clang++, make)	6m 43s
unix (macos-14, clang++, cmake)	7m 52s
windows-mingw-testing (windows-2019, 32)	4m 27s
windows-mingw-testing (windows-2019, 64)	3m 45s
windows-mingw-testing (windows-2022, 32)	4m 50s
windows-mingw-testing (windows-2022, 64)	4m 20s
	2h 0m 50s

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