`no_std` support #82

Job	Run time
build	36s
verify-proof (dex)	24s
Test no_std support (dex)	4m 53s
verify-proof (recursive)	52s
Test no_std support (recursive)	4m 45s
verify-proof (recursive_with_poseidon)	48s
Test no_std support (recursive_with_poseidon)	4m 54s
verify-proof (small)	28s
Test no_std support (small)	4m 50s
verify-proof (starknet)	1m 35s
Test no_std support (starknet)	3m 53s
Test no_std support (starknet_with_keccak)	4m 19s
verify-proof (starknet_with_keccak)	35s
	32m 52s

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