ICU-22939 DRAFT: WIP on function composition #2965

Job	Run time
clang-valgrind-intltest (utility)	6m 40s
clang-valgrind-test	10m 7s
clang-valgrind-intltest (normalize)	6m 18s
clang-valgrind-intltest (collator)	5m 26s
clang-valgrind-intltest (regex)	5m 36s
clang-valgrind-intltest (format)	16m 25s
clang-valgrind-intltest (translit)	5m 42s
clang-valgrind-intltest (rbbi)	7m 37s
clang-valgrind-intltest (rbnf)	6m 15s
clang-valgrind-intltest (rbnfrt)	6m 8s
clang-valgrind-intltest (icuserv)	5m 4s
clang-valgrind-intltest (idna)	5m 7s
clang-valgrind-intltest (convert)	6m 45s
clang-valgrind-intltest (rbnfp)	5m 31s
clang-valgrind-intltest (csdet)	5m 5s
clang-valgrind-intltest (spoof)	5m 28s
clang-valgrind-intltest (bidi)	5m 19s
	1h 54m 33s

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