ICU-22549 Add UnicodeSet fuzzer #1248

Job	Run time
clang-valgrind-intltest (utility)	6m 39s
clang-valgrind-test	10m 13s
clang-valgrind-intltest (normalize)	6m 24s
clang-valgrind-intltest (collator)	5m 20s
clang-valgrind-intltest (regex)	5m 30s
clang-valgrind-intltest (format)	16m 22s
clang-valgrind-intltest (translit)	5m 57s
clang-valgrind-intltest (rbbi)	7m 22s
clang-valgrind-intltest (rbnf)	6m 13s
clang-valgrind-intltest (rbnfrt)	6m 23s
clang-valgrind-intltest (icuserv)	5m 16s
clang-valgrind-intltest (idna)	5m 13s
clang-valgrind-intltest (convert)	6m 33s
clang-valgrind-intltest (rbnfp)	5m 30s
clang-valgrind-intltest (csdet)	5m 8s
clang-valgrind-intltest (spoof)	4m 55s
clang-valgrind-intltest (bidi)	5m 45s
	1h 54m 43s

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