ICU-23000 Replace CharString for LocaleBased #3281

Job	Run time
clang-valgrind-intltest (utility)	6m 26s
clang-valgrind-test	10m 25s
clang-valgrind-intltest (normalize)	6m 44s
clang-valgrind-intltest (collator)	5m 30s
clang-valgrind-intltest (regex)	5m 35s
clang-valgrind-intltest (format)	8m 5s
clang-valgrind-intltest (translit)	6m 11s
clang-valgrind-intltest (rbbi)	7m 42s
clang-valgrind-intltest (rbnf)	6m 38s
clang-valgrind-intltest (rbnfrt)	6m 18s
clang-valgrind-intltest (icuserv)	5m 34s
clang-valgrind-intltest (idna)	5m 33s
clang-valgrind-intltest (convert)	6m 56s
clang-valgrind-intltest (rbnfp)	5m 39s
clang-valgrind-intltest (csdet)	5m 45s
clang-valgrind-intltest (spoof)	5m 16s
clang-valgrind-intltest (bidi)	5m 59s
	1h 50m 16s

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