Calculate actual receiptsRoot when possible

[georgi-l95]

Problem

Currently when we return block information, we don't include actual receiptsRoot, this is because Hedera is not using Merkle Patricia trie. However this can be easly calucalted during processing of the request. Returning real receiptsRoot can help tools, as well as help developers use merkle proofs of inclusion.

Solution

Taking a look at how calculating receiptsRoot is done in the javascript execution client for ethereum can help us do it here as well. More information about the implementation can be found here.