unpack_strategy/directory: use mv for nested unpack #30834

Job	Run time
syntax	39s
vendored gems	34s
cask audit	3m 17s
formula audit	4m 13s
tap syntax	6m 41s
test default formula (Ubuntu 22.04)	1m 31s
tests (online)	9m 41s
test default formula (Ubuntu 20.04)	3m 26s
update-test (Ubuntu 22.04)	15s
test default formula (macOS 13 x86_64)	3m 23s
tests (generic OS)	2m 57s
update-test (macOS)	25s
tests (Ubuntu 22.04)	3m 3s
test default formula (macOS 15 arm64)	1m 17s
tests (Ubuntu 20.04)	3m 42s
tests (macOS 13 x86_64)	9m 55s
tests (macOS 15 arm64)	4m 55s
	59m 54s

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