Support older contract state in eth_getStorageAt

[georgi-l95]

With the refactoring performed in this PR we now support:

• Current state of a contract
• Previous state of a contract a contract, if we know the exact block number this state change has been made.

We are missing support of:

• Previous state of a contract, without specifying the exact block number this change occurred. For example we pass a block number and return the state of the contract prior this block number.

This might require some changes to the mirror-node endpoint, for example support of timestamp.
Only way to do it directly in the relay is to search every block before the one we pass as parameter in search for this change. This is highly unoptimised and not a solution.

[georgi-l95]

Waiting for hashgraph/hedera-mirror-node#5517 to be merged.