ICU-22902 Remove support for Unsupported, Private & Reserved constructs #2871

Job	Run time
clang-valgrind-intltest (utility)	6m 32s
clang-valgrind-test	10m 41s
clang-valgrind-intltest (normalize)	6m 58s
clang-valgrind-intltest (collator)	5m 19s
clang-valgrind-intltest (regex)	5m 29s
clang-valgrind-intltest (format)	16m 4s
clang-valgrind-intltest (translit)	6m 30s
clang-valgrind-intltest (rbbi)	8m 38s
clang-valgrind-intltest (rbnf)	6m 55s
clang-valgrind-intltest (rbnfrt)	6m 6s
clang-valgrind-intltest (icuserv)	5m 5s
clang-valgrind-intltest (idna)	5m 13s
clang-valgrind-intltest (convert)	6m 54s
clang-valgrind-intltest (rbnfp)	5m 4s
clang-valgrind-intltest (csdet)	5m 4s
clang-valgrind-intltest (spoof)	5m 51s
clang-valgrind-intltest (bidi)	5m 9s
	1h 57m 32s

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