tests

Optionally disable c bindings #198

Job	Run time
kzg_ci	41s
backend_ci (ubuntu-latest, blst)	13m 36s
backend_ci (ubuntu-latest, zkcrypto)	31m 26s
backend_ci (ubuntu-latest, arkworks)	19m 46s
backend_ci (ubuntu-latest, arkworks3)	17m 19s
backend_ci (ubuntu-latest, constantine)	24m 29s
backend_ci (windows-latest, blst)	4m 54s
backend_ci (windows-latest, zkcrypto)	8m 12s
backend_ci (windows-latest, arkworks)	6m 38s
backend_ci (windows-latest, arkworks3)	5m 34s
backend_ci (windows-latest, constantine)	8m 1s
backend_ci (macos-latest, blst)	5m 49s
backend_ci (macos-latest, zkcrypto)	9m 2s
backend_ci (macos-latest, arkworks)	6m 11s
backend_ci (macos-latest, arkworks3)	7m 12s
backend_ci (macos-latest, constantine)	8m 53s
	2h 57m 43s

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