feat: resolve #12, add client caching and lazy evaluation

[Soham-ent]

Closes #12.

While adding the Chainlink summary generation, I noticed a few areas in the data pipeline that could be optimized for local development and memory usage.

• Generalized the Pyth summary logic using a 'providerSummaries' config to automatically support Chainlink, Chronicle, RedStone, etc.
• Added a 'clientCache' map to 'getClient.ts' to memoize Viem instances and prevent redundant client instantiations.
• Switched 'publicClient' in 'chainConfigs.ts' to use getters for lazy evaluation. This prevents local environments from crashing on startup if a developer is missing a specific network's 'RPC_URL' in their '.env'.

Tested locally against mainnet.