Fix #14941: FN memleak with `_create_locale` #20507

Job	Run time
build_cmake (alpine:3.23, false, false)	4m 26s
build_cmake (ubuntu:25.10, true, true)	5m 35s
build_cmake (ubuntu:24.04, true, true)	5m 41s
build_make (ubuntu:24.04)	4m 47s
build_make (ubuntu:25.10)	5m 13s
build_make (alpine:3.23)	6m 17s
	31m 59s

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