State Change Indexer: Add Contract Cache Store and DB Tables

[aditya1702]

This is an optimization where we store a DB backend in-memory cache:

contractID : {
      name
      symbol
      expiry
}

This helps store the name and symbol values for contract tokens and avoid calling the simulation endpoint on RPC each time to fetch the information. Each item will have an expiry after which we will refresh the cache again using simulateTransaction calls.

We will also store the mapping in the postgres table to prevent loss of in-memory cache in case of restarts/shutdowns