Improve Fetching of Contract Currency Details

What's Changed

Improve Fetching of Contract Currency Details.

Motivation

To improve /block latency. A major bottleneck is that contractCurrencyMap is created fresh for each transaction, so it only caches within a single transaction's logs. That's why we see repeated GetContractCurrency calls for the same contracts across different transactions.

Solution

Add an LRU cache that stores contract currency details across blocks. Also, don't go to the node for allow listed tokens to get symbol and decimals (if env var USE_TOKEN_WHITE_LIST_METADATA="true"), as they can be retrieved from the config.

New Contributors

• @marklandgrebe-cb made their first contribution in #136

Full Changelog: v0.0.18...v0.0.19