ICU-23000 Replace CharString for LocaleBased #3259

Job	Run time
clang-valgrind-test	10m 8s
clang-valgrind-intltest (utility)	6m 49s
clang-valgrind-intltest (normalize)	6m 17s
clang-valgrind-intltest (collator)	5m 22s
clang-valgrind-intltest (regex)	5m 21s
clang-valgrind-intltest (format)	16m 25s
clang-valgrind-intltest (translit)	6m 43s
clang-valgrind-intltest (rbbi)	8m 8s
clang-valgrind-intltest (rbnf)	6m 31s
clang-valgrind-intltest (rbnfrt)	6m 32s
clang-valgrind-intltest (icuserv)	5m 13s
clang-valgrind-intltest (idna)	5m 25s
clang-valgrind-intltest (convert)	7m 0s
clang-valgrind-intltest (rbnfp)	5m 28s
clang-valgrind-intltest (csdet)	5m 36s
clang-valgrind-intltest (spoof)	5m 37s
clang-valgrind-intltest (bidi)	5m 36s
	1h 58m 11s

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