tests: Use git::copy_tracked_files from test-helper #3404

Job	Run time
test (stable)	3m 28s
test (1.26)	7m 7s
test (beta)	3m 28s
test (1.30)	5m 10s
test (nightly)	3m 28s
test (no rustup)	2m 2s
test (nightly, macos-latest)	3m 12s
test (1.31)	5m 22s
test (nightly, windows-latest)	5m 23s
test (1.36)	6m 26s
test (1.39)	6m 13s
test (1.41)	6m 11s
release-dry-run / prepare	2s
miri / miri	52s
msrv / prepare	4s
tidy / prepare	3s
release-dry-run / build (aarch64-unknown-linux-gnu, ubuntu-22.04)	1m 9s
release-dry-run / build (aarch64-unknown-linux-musl)	50s
release-dry-run / build (aarch64-apple-darwin, macos-13)	1m 40s
release-dry-run / build (aarch64-pc-windows-msvc, windows-2019)	2m 29s
release-dry-run / build (x86_64-unknown-linux-gnu, ubuntu-22.04)	42s
release-dry-run / build (x86_64-unknown-linux-musl)	45s
release-dry-run / build (x86_64-apple-darwin, macos-13)	1m 44s
release-dry-run / build (x86_64-pc-windows-msvc, windows-2019)	2m 14s
release-dry-run / build (x86_64-unknown-freebsd)	1m 6s
release-dry-run / build (x86_64-unknown-illumos)	48s
release-dry-run / build (universal-apple-darwin, macos-13)	1m 18s
tidy / tidy	54s
tidy / clippy	20s
tidy / check-external-types	0s
tidy / deny	15s
tidy / codegen	0s
tidy / docs	0s
msrv / build (ubuntu-latest)	5m 24s
msrv / build (windows-latest)	8m 4s
	1h 28m 13s

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