Add contract metadata fetching service

[aditya1702]

What

• Add a contract metadata service that simulates and fetches the name, symbol and decimals for contract tokens
• Add relevant unit tests
• Call this new service during initial checkpoint population and at the end of ingestion loop (if there are new contract tokens to ingest). However, we dont stall ingestion on simulation errors and instead just fail gracefully.

Why

This helps keep our contract tokens db updated with the code, issuer, name, symbol and decimals info for unique contract tokens and we dont have to simulate during account balance fetch.

Known limitations

N/A

Issue that this PR addresses

Closes #392