feat: add buffer store LRU cache

[alanshaw]

Adds a LRU cache to the buffer store.

Typically the same lambda instance is invoked multiple times to create the aggregate. Every time it is executed it needs to load details of all the currently buffered pieces. This PR adds an LRU cache to speed up the process.

[seed-deploy]

View stack outputs

• pr106-w3filecoin-ApiStack

  Name	Value
  AggregatorApiCustomDomain	https://pr106.aggregator.web3.storage
  AggregatorApiEndpoint	https://jkc3g9t8gi.execute-api.us-east-2.amazonaws.com
  DealerApiCustomDomain	https://pr106.dealer.web3.storage
  DealerApiEndpoint	https://yh8nrjvt2m.execute-api.us-east-2.amazonaws.com
  DealTrackerApiCustomDomain	https://pr106.tracker.web3.storage
  DealTrackerApiEndpoint	https://ysprnowg22.execute-api.us-east-2.amazonaws.com

• pr106-w3filecoin-DataStack

  Name	Value
  AggregatorAggregateTableName	pr106-w3filecoin-aggregator-aggregate-store
  AggregatorBufferBucketName	pr106-w3filecoin-aggregator-buffer-store-0
  AggregatorInclusionProofBucketName	pr106-w3filecoin-aggregator-inclusion-proof-store-0
  AggregatorInclusionTableName	pr106-w3filecoin-aggregator-inclusion-store
  AggregatorPieceTableName	pr106-w3filecoin-aggregator-piece-store
  DealerAggregateStoreTableName	pr106-w3filecoin-dealer-aggregate-store
  DealerOfferStoreBucketName	pr106-w3filecoin-dealer-offer-store-0
  DealTrackerDealArchiveBucketName	pr106-w3filecoin-deal-tracker-deal-archive-store-1
  DealTrackerDealStoreTableName	pr106-w3filecoin-deal-tracker-deal-store-v1

• pr106-w3filecoin-AggregatorStack

• pr106-w3filecoin-DealerStack

• pr106-w3filecoin-DealTrackerStack