[Tech Debt] Optimize parallel requests for token/contracts

[hectorgomezv]

Description

Context

The async nature of the CGW causes the service to send several requests to the Safe Transaction Service in parallel for the same data, so only after the first one gets a response is the result cached.

This is especially problematic when the CGW requests the tokens/contracts for all the transactions on a page, and the same token/contract is repeated many times on that page. This causes the CGW to request the same token/contract N times (before receiving any response from the Transaction Service) instead of 1 for each repeated token/contract.

Requirements

• Collect a Set (no repeated items) before sending the requests to the Safe Transaction Service.
• Wait for the requests in the Set to be fulfilled/rejected. Subsequent calls will be cached.

Examples