contracts: calldata encryption function (Solidity)

[CedarMist]

Closes: #436

Implements calldata encryption to create encrypted transactions from contracts on Sapphire.

This also updates Cipher TS to accept an optional nonce parameter, this means we can do easier deterministic tests to verify the Solidity implementation matches the Typescript implementation.

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[rube-de]

Running the test against localnet fails for me

  1) CalldataEncryption
       testEncryptCallData:

      AssertionError: expected '0xa264626f6479a462706b58204a0269de680…' to equal '0xa264626f6479a462706b58204a0269de680…'
      + expected - actual

      -0xa264626f6479a462706b58204a0269de680edc05553943543d70c5df9e23f6af53381eded9641b5d08df7b2d646461746158184bf966b9e87a715c26b2428996c85589e1ba7e2c060487206565706f636800656e6f6e63654fb9cb3f82f8a608902dcb321ae611a766666f726d617401
      +0xa264626f6479a462706b58204a0269de680edc05553943543d70c5df9e23f6af53381eded9641b5d08df7b2d64646174615818cbca0d4444a619c839a845d2b045ccf4437a861047e59b5f6565706f636800656e6f6e63654f0d0922c9861097bab82a5a77b15d8666666f726d617401
      
       at Context.<anonymous> (test/calldata.spec.ts:50:22)

[CedarMist]

That could happen if you don't build the clients/js package, the solidity tests require repeatability so I had to modify the client to pass a custom nonce.

If the clients/js package isn't rebuilt, the solidity tests will use the last build you did which will generate a nonce every time and ignore the one passed in.