tests

Add mcl backend #240

Job	Run time
kzg_ci	44s
backend_ci (ubuntu-latest, blst)	15m 36s
backend_ci (ubuntu-latest, zkcrypto)	32m 15s
backend_ci (ubuntu-latest, arkworks5)	17m 49s
backend_ci (ubuntu-latest, arkworks4)	19m 51s
backend_ci (ubuntu-latest, arkworks3)	10m 29s
backend_ci (ubuntu-latest, constantine)	26m 17s
backend_ci (ubuntu-latest, mcl)	15m 49s
backend_ci (windows-latest, blst)	5m 40s
backend_ci (windows-latest, zkcrypto)	9m 13s
backend_ci (windows-latest, arkworks5)	6m 20s
backend_ci (windows-latest, arkworks4)	6m 46s
backend_ci (windows-latest, arkworks3)	6m 47s
backend_ci (windows-latest, constantine)	11m 4s
backend_ci (macos-latest, blst)	6m 40s
backend_ci (macos-latest, zkcrypto)	7m 52s
backend_ci (macos-latest, arkworks5)	6m 3s
backend_ci (macos-latest, arkworks4)	6m 18s
backend_ci (macos-latest, arkworks3)	6m 13s
backend_ci (macos-latest, constantine)	11m 37s
backend_ci (macos-latest, mcl)	6m 33s
	3h 55m 56s

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