[TM-17] Make contract's address computation more correct

Description

Problem: we have 'contractAddress' function to compute address of a contract. However, it returns a constant value, which is also invalid. Solution: implement address computation in a similar way to what Tezos reference implementation does based on this stackexchange answer¹. Since we don't know precise binary format yet, it uses JSON serialization as the easiest solution. We don't need to be precisely compatible with Tezos at this point.

¹ https://tezos.stackexchange.com/a/361/342

Related issue(s)

https://issues.serokell.io/issue/TM-17

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