tests

Constantine backend #62

Job	Run time
tests (ubuntu-latest, blst)	7m 56s
tests (ubuntu-latest, zkcrypto)	54s
tests (ubuntu-latest, arkworks)	9m 33s
tests (ubuntu-latest, constantine)	9m 5s
tests (windows-latest, blst)	3m 31s
tests (windows-latest, zkcrypto)	2m 57s
tests (windows-latest, arkworks)	4m 35s
tests (windows-latest, constantine)	5m 31s
tests (macos-11, blst)	5m 0s
tests (macos-11, zkcrypto)	3m 24s
tests (macos-11, arkworks)	6m 42s
tests (macos-11, constantine)	20m 25s
	1h 19m 33s

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