Fix #14941: FN memleak with `_create_locale` #20502

Job	Run time
build_make (ubuntu:24.04)	5m 35s
build_cmake (alpine:3.23, false, false)	4m 44s
build_make (alpine:3.23)	5m 58s
build_make (ubuntu:25.10)	4m 37s
build_cmake (ubuntu:25.10, true, true)	5m 56s
build_cmake (ubuntu:24.04, true, true)	6m 1s
	32m 51s

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