Scarb expand initial impl #5949

Job	Run time
build test linux x86-64	3m 17s
check-rust	3m 42s
build test windows x86-64	5m 38s
check-website	13s
scarb-metadata compatibility check	41s
doc tests	3m 4s
test linux x86-64 1/8	6m 18s
test linux x86-64 2/8	10m 32s
test linux x86-64 3/8	8m 27s
test linux x86-64 4/8	6m 0s
test linux x86-64 5/8	5m 40s
test linux x86-64 6/8	4m 2s
test linux x86-64 7/8	4m 15s
test linux x86-64 8/8	2m 45s
test windows x86-64 1/8	6m 0s
test windows x86-64 2/8	8m 0s
test windows x86-64 3/8	7m 25s
test windows x86-64 4/8	6m 9s
test windows x86-64 5/8	5m 45s
test windows x86-64 6/8	4m 55s
test windows x86-64 7/8	6m 59s
test windows x86-64 8/8	4m 35s
	1h 54m 22s

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