ICU-22940 MF2 ICU4C: Error checking improvements in parser #3215

Job	Run time
clang-valgrind-intltest (utility)	6m 42s
clang-valgrind-intltest (normalize)	6m 30s
clang-valgrind-intltest (collator)	5m 20s
clang-valgrind-intltest (regex)	5m 21s
clang-valgrind-intltest (format)	16m 27s
clang-valgrind-intltest (translit)	6m 5s
clang-valgrind-test	10m 14s
clang-valgrind-intltest (rbbi)	7m 58s
clang-valgrind-intltest (rbnf)	6m 24s
clang-valgrind-intltest (rbnfrt)	6m 21s
clang-valgrind-intltest (icuserv)	5m 33s
clang-valgrind-intltest (idna)	5m 23s
clang-valgrind-intltest (convert)	6m 45s
clang-valgrind-intltest (rbnfp)	5m 18s
clang-valgrind-intltest (csdet)	5m 17s
clang-valgrind-intltest (spoof)	5m 23s
clang-valgrind-intltest (bidi)	5m 33s
	1h 56m 34s

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