WASM: add decryption methods to MerkleNote #2526

Job	Run time
Check Rust	7m 4s
Vet Dependencies	2m 47s
Test ironfish-rust (1/2)	6m 18s
Test ironfish-rust (2/2)	6m 1s
Test ironfish-rust (no default features) (1/2)	1m 19s
Test ironfish-rust-wasm	1m 56s
Test ironfish-rust (all features) (1/2)	3m 34s
Test ironfish-rust (no default features) (2/2)	1m 22s
Test ironfish-rust (all features) (2/2)	3m 23s
Test ironfish-zkp	2m 0s
Lint Rust	1m 16s
	37m 0s

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