ICU-22939 DRAFT: WIP on function composition #2958

Job	Run time
clang-valgrind-test	2m 12s
clang-valgrind-intltest (utility)	2m 29s
clang-valgrind-intltest (normalize)	2m 11s
clang-valgrind-intltest (collator)	2m 23s
clang-valgrind-intltest (regex)	2m 20s
clang-valgrind-intltest (format)	2m 32s
clang-valgrind-intltest (translit)	2m 10s
clang-valgrind-intltest (rbbi)	2m 23s
clang-valgrind-intltest (rbnf)	2m 8s
clang-valgrind-intltest (rbnfrt)	2m 34s
clang-valgrind-intltest (icuserv)	2m 29s
clang-valgrind-intltest (idna)	2m 20s
clang-valgrind-intltest (convert)	2m 25s
clang-valgrind-intltest (rbnfp)	2m 34s
clang-valgrind-intltest (csdet)	2m 20s
clang-valgrind-intltest (spoof)	2m 35s
clang-valgrind-intltest (bidi)	2m 24s
	40m 29s

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