tests

Constantine backend #48

Job	Run time
tests (ubuntu-latest, blst)	7m 29s
tests (ubuntu-latest, zkcrypto)	50s
tests (ubuntu-latest, arkworks)	10m 6s
tests (ubuntu-latest, constantine)	3m 32s
tests (windows-latest, blst)	3m 37s
tests (windows-latest, zkcrypto)	2m 42s
tests (windows-latest, arkworks)	4m 31s
tests (windows-latest, constantine)	5m 16s
tests (macos-11, blst)	4m 32s
tests (macos-11, zkcrypto)	3m 25s
tests (macos-11, arkworks)	5m 46s
tests (macos-11, constantine)	18m 54s
	1h 10m 40s

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