unpack_strategy/directory: use mv for nested unpack #30836

Job	Run time
syntax	41s
vendored gems	36s
cask audit	2m 22s
formula audit	4m 40s
tap syntax	5m 59s
test default formula (Ubuntu 22.04)	1m 36s
tests (online)	5m 32s
test default formula (Ubuntu 20.04)	2m 56s
update-test (Ubuntu 22.04)	27s
tests (generic OS)	2m 59s
test default formula (macOS 13 x86_64)	3m 34s
update-test (macOS)	24s
tests (Ubuntu 22.04)	2m 57s
test default formula (macOS 15 arm64)	1m 27s
tests (Ubuntu 20.04)	4m 5s
tests (macOS 13 x86_64)	7m 14s
tests (macOS 15 arm64)	4m 30s
	51m 59s

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