tests: Use git::copy_tracked_files from test-helper #3403

Job	Run time
test (stable)	15s
test (no rustup)	31s
test (beta)	26s
test (1.26)	22s
test (nightly)	25s
test (1.30)	19s
test (nightly, macos-latest)	33s
test (1.31)	21s
test (nightly, windows-latest)	47s
test (1.36)	23s
test (1.39)	22s
test (1.41)	22s
miri / miri	52s
msrv / prepare	4s
release-dry-run / prepare	4s
tidy / prepare	2s
tidy / clippy	20s
tidy / deny	13s
tidy / check-external-types	0s
tidy / codegen	0s
tidy / docs	0s
tidy / tidy	59s
msrv / build (ubuntu-latest)	5m 45s
msrv / build (windows-latest)	7m 37s
release-dry-run / build (aarch64-unknown-linux-gnu, ubuntu-22.04)	58s
release-dry-run / build (aarch64-unknown-linux-musl)	50s
release-dry-run / build (aarch64-apple-darwin, macos-13)	1m 14s
release-dry-run / build (aarch64-pc-windows-msvc, windows-2019)	2m 38s
release-dry-run / build (x86_64-unknown-linux-gnu, ubuntu-22.04)	48s
release-dry-run / build (x86_64-unknown-linux-musl)	44s
release-dry-run / build (x86_64-apple-darwin, macos-13)	2m 8s
release-dry-run / build (x86_64-pc-windows-msvc, windows-2019)	2m 23s
release-dry-run / build (x86_64-unknown-freebsd)	58s
release-dry-run / build (x86_64-unknown-illumos)	49s
release-dry-run / build (universal-apple-darwin, macos-13)	1m 40s
	36m 12s

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