ICU-22939 DRAFT: WIP on function composition #3006

Job	Run time
clang-valgrind-test	11m 3s
clang-valgrind-intltest (utility)	6m 56s
clang-valgrind-intltest (normalize)	6m 40s
clang-valgrind-intltest (collator)	5m 21s
clang-valgrind-intltest (regex)	5m 49s
clang-valgrind-intltest (format)	16m 24s
clang-valgrind-intltest (translit)	6m 6s
clang-valgrind-intltest (rbbi)	7m 28s
clang-valgrind-intltest (rbnf)	6m 47s
clang-valgrind-intltest (rbnfrt)	7m 7s
clang-valgrind-intltest (icuserv)	5m 41s
clang-valgrind-intltest (idna)	5m 35s
clang-valgrind-intltest (convert)	6m 52s
clang-valgrind-intltest (rbnfp)	5m 34s
clang-valgrind-intltest (csdet)	5m 29s
clang-valgrind-intltest (spoof)	6m 2s
clang-valgrind-intltest (bidi)	5m 45s
	2h 0m 39s

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