Implement stringByFoldingWithOptions #2947

Job	Run time
Windows x64 MSVC Clang gnustep-2.2	19m 40s
Ubuntu x64 Clang gnustep-2.2	5m 12s
Windows x64 MinGW GCC	27m 14s
Windows x64 MinGW Clang gnustep-2.2	24m 50s
Rocky Linux 8 x64 Clang gnustep-2.2	2m 51s
Rocky Linux 9 x64 Clang gnustep-2.2	16m 21s
Windows arm64 MSVC Clang gnustep-2.2	37m 54s
Ubuntu x64 GCC	5m 9s
	2h 19m 11s

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