ICU-22954 revert making LocalPointer & Co. header-only #3243

Job	Run time
clang-valgrind-intltest (utility)	6m 56s
clang-valgrind-intltest (normalize)	6m 26s
clang-valgrind-intltest (collator)	5m 28s
clang-valgrind-test	10m 19s
clang-valgrind-intltest (regex)	5m 43s
clang-valgrind-intltest (format)	16m 21s
clang-valgrind-intltest (translit)	6m 10s
clang-valgrind-intltest (rbbi)	8m 10s
clang-valgrind-intltest (rbnf)	6m 37s
clang-valgrind-intltest (rbnfrt)	6m 16s
clang-valgrind-intltest (icuserv)	5m 21s
clang-valgrind-intltest (idna)	5m 18s
clang-valgrind-intltest (convert)	7m 2s
clang-valgrind-intltest (rbnfp)	5m 31s
clang-valgrind-intltest (csdet)	5m 17s
clang-valgrind-intltest (spoof)	5m 24s
clang-valgrind-intltest (bidi)	5m 51s
	1h 58m 10s

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