tests

Add mcl backend #224

Job	Run time
kzg_ci	44s
backend_ci (ubuntu-latest, blst)	15m 23s
backend_ci (ubuntu-latest, zkcrypto)	32m 47s
backend_ci (ubuntu-latest, arkworks5)	19m 21s
backend_ci (ubuntu-latest, arkworks4)	20m 49s
backend_ci (ubuntu-latest, arkworks3)	6m 21s
backend_ci (ubuntu-latest, constantine)	28m 4s
backend_ci (ubuntu-latest, mcl)	5m 35s
backend_ci (windows-latest, blst)	5m 14s
backend_ci (windows-latest, zkcrypto)	9m 30s
backend_ci (windows-latest, arkworks5)	6m 36s
backend_ci (windows-latest, arkworks4)	7m 42s
backend_ci (windows-latest, arkworks3)	7m 50s
backend_ci (windows-latest, constantine)	9m 57s
backend_ci (windows-latest, mcl)	3m 8s
backend_ci (macos-latest, blst)	6m 50s
backend_ci (macos-latest, zkcrypto)	9m 0s
backend_ci (macos-latest, arkworks5)	6m 53s
backend_ci (macos-latest, arkworks4)	8m 18s
backend_ci (macos-latest, arkworks3)	7m 8s
backend_ci (macos-latest, constantine)	14m 6s
backend_ci (macos-latest, mcl)	7m 0s
	3h 58m 16s

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