Migrate Scarb to per-crate compiler plugins #8257

Job	Run time
scarb-metadata compatibility check	46s
check-website	11s
build test linux x86-64	4m 22s
check-rust	4m 23s
build test windows x86-64	9m 31s
doc tests	3m 24s
test linux x86-64 1/8	21m 40s
test linux x86-64 2/8	25m 45s
test linux x86-64 3/8	20m 34s
test linux x86-64 4/8	18m 21s
test linux x86-64 5/8	15m 58s
test linux x86-64 6/8	16m 1s
test linux x86-64 7/8	12m 4s
test linux x86-64 8/8	14m 41s
test windows x86-64 1/8	19m 31s
test windows x86-64 2/8	22m 57s
test windows x86-64 3/8	19m 52s
test windows x86-64 4/8	15m 33s
test windows x86-64 5/8	15m 52s
test windows x86-64 6/8	14m 42s
test windows x86-64 7/8	11m 53s
test windows x86-64 8/8	13m 50s
	5h 1m 51s

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