Migrate Scarb to per-crate compiler plugins #8255

Job	Run time
check-website	18s
scarb-metadata compatibility check	41s
check-rust	4m 35s
build test linux x86-64	8m 27s
build test windows x86-64	23m 25s
doc tests	3m 15s
test linux x86-64 1/8	16m 38s
test linux x86-64 2/8	25m 38s
test linux x86-64 3/8	20m 34s
test linux x86-64 4/8	18m 42s
test linux x86-64 5/8	15m 48s
test linux x86-64 6/8	16m 16s
test linux x86-64 7/8	12m 14s
test linux x86-64 8/8	15m 11s
test windows x86-64 1/8	14m 48s
test windows x86-64 2/8	22m 45s
test windows x86-64 3/8	19m 45s
test windows x86-64 4/8	15m 56s
test windows x86-64 5/8	15m 56s
test windows x86-64 6/8	14m 37s
test windows x86-64 7/8	11m 19s
test windows x86-64 8/8	14m 0s
	5h 10m 48s

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