ICU-22549 Add DateTimePatternGenerator fuzzer #1216

Job	Run time
clang-valgrind-intltest (utility)	6m 44s
clang-valgrind-test	10m 12s
clang-valgrind-intltest (normalize)	6m 3s
clang-valgrind-intltest (collator)	5m 1s
clang-valgrind-intltest (regex)	4m 49s
clang-valgrind-intltest (format)	16m 13s
clang-valgrind-intltest (translit)	5m 52s
clang-valgrind-intltest (rbbi)	7m 21s
clang-valgrind-intltest (rbnf)	6m 3s
clang-valgrind-intltest (rbnfrt)	6m 10s
clang-valgrind-intltest (icuserv)	4m 54s
clang-valgrind-intltest (idna)	5m 26s
clang-valgrind-intltest (convert)	6m 48s
clang-valgrind-intltest (rbnfp)	5m 2s
clang-valgrind-intltest (csdet)	5m 12s
clang-valgrind-intltest (spoof)	4m 53s
clang-valgrind-intltest (bidi)	5m 25s
	1h 52m 8s

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