Rust

Add zk-nullifier example and reorganize zk/ folder #140

Job	Run time
create-and-update	1m 26s
counter/pinocchio	1m 26s
zk/zk-nullifier	6m 6s
counter/native	1m 26s
zk/zk-id	6m 30s
basic-operations/native/native-program-reinit	1m 14s
basic-operations/native/native-program-close	1m 15s
account-comparison	1m 23s
basic-operations/native/native-program-create	1m 24s
basic-operations/native/native-program-update	1m 17s
airdrop-implementations/simple-claim/program	5m 41s
zk/zk-merkle-proof	2m 12s
basic-operations/native/native-program-burn	1m 16s
	32m 36s

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