Rename test plugin to `cairo_test` #5977

Job	Run time
build test linux x86-64	3m 19s
scarb-metadata compatibility check	35s
build test windows x86-64	6m 8s
doc tests	3m 3s
check-rust	3m 36s
check-website	12s
test linux x86-64 1/8	6m 24s
test linux x86-64 2/8	9m 0s
test linux x86-64 3/8	8m 35s
test linux x86-64 4/8	6m 9s
test linux x86-64 5/8	5m 58s
test linux x86-64 6/8	4m 11s
test linux x86-64 7/8	4m 34s
test linux x86-64 8/8	2m 50s
test windows x86-64 1/8	6m 37s
test windows x86-64 2/8	10m 58s
test windows x86-64 3/8	8m 1s
test windows x86-64 4/8	6m 0s
test windows x86-64 5/8	6m 37s
test windows x86-64 6/8	5m 4s
test windows x86-64 7/8	4m 8s
test windows x86-64 8/8	3m 56s
	1h 55m 55s

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