Deterministic (de-randomized) state encryption & randomness

To enable multi-enclave endorsement, state encryption should be deterministic (so we can handle multi-enclave endorsement policies) yet should still provide semantic security which implies randomized encryption. Additionally, we should be careful with bounds on numbers of encryption per key where in our case an enclave might be easily used as a fast "encryption-oracle".

Additionally, solving above also should enable a secure way to provide chaincode access to (pseudo-)random values, something which is generally very difficult to achieve in "normal" smart contracts but unlocks additional smart contract functionalities.