Rust

Add zk-nullifier example and reorganize zk/ folder #157

Job	Run time
basic-operations/native/native-program-close	1m 17s
create-and-update	1m 38s
basic-operations/native/native-program-create	1m 20s
zk/zk-nullifier	53s
basic-operations/native/native-program-update	1m 17s
zk/zk-id	1m 30s
basic-operations/native/native-program-burn	1m 22s
counter/native	1m 14s
account-comparison	1m 15s
basic-operations/native/native-program-reinit	1m 36s
zk/zk-merkle-proof	1m 0s
airdrop-implementations/simple-claim/program	4m 56s
counter/pinocchio	1m 19s
	20m 37s

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