Move helpers from contracts to common-ts

[davekaj]

The function here:

https://github.com/graphprotocol/contracts/blob/master/scripts/contracts/connectedContracts.ts

Can be moved here. I think the simple function like staking are probably duplicated and can be removed. But this is what I think is valuable:

• EthereumDID registry functions - this will help nena in the front end with Account Metadata, Subgraph Metadata, and Version metadata handling
• creating new subgraphs and new subgraph versions - This will also help in the front end

All other functions are probably duplicate. If not , they are simple and we can add them

[davekaj]

@nenadjaja @Jannis