Rust

Add zk-nullifier example and reorganize zk/ folder #149

Job	Run time
zk/zk-id	6m 44s
basic-operations/native/native-program-create	1m 41s
account-comparison	1m 17s
zk/zk-nullifier	6m 9s
basic-operations/native/native-program-update	1m 26s
counter/native	1m 16s
create-and-update	1m 49s
counter/pinocchio	1m 35s
basic-operations/native/native-program-reinit	1m 18s
basic-operations/native/native-program-burn	1m 26s
basic-operations/native/native-program-close	1m 21s
airdrop-implementations/simple-claim/program	5m 22s
zk/zk-merkle-proof	2m 49s
	34m 13s

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