ICU-22991 Simplified Grego code #3330

Job	Run time
clang-valgrind-intltest (utility)	6m 57s
clang-valgrind-test	10m 24s
clang-valgrind-intltest (normalize)	6m 2s
clang-valgrind-intltest (collator)	5m 14s
clang-valgrind-intltest (regex)	5m 27s
clang-valgrind-intltest (format)	16m 37s
clang-valgrind-intltest (translit)	6m 0s
clang-valgrind-intltest (rbbi)	8m 20s
clang-valgrind-intltest (rbnf)	6m 17s
clang-valgrind-intltest (rbnfrt)	6m 20s
clang-valgrind-intltest (icuserv)	5m 35s
clang-valgrind-intltest (idna)	5m 29s
clang-valgrind-intltest (convert)	7m 7s
clang-valgrind-intltest (rbnfp)	5m 13s
clang-valgrind-intltest (csdet)	5m 32s
clang-valgrind-intltest (spoof)	5m 23s
clang-valgrind-intltest (bidi)	5m 39s
	1h 57m 36s

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