add new simple storage classes + remove graph storage classes

packages/core/package.json

packages/core/src/dataStructs.ts

packages/core/src/storage/FileSystem.ts

packages/core/src/storage/StorageContext.ts

packages/core/src/storage/constants.ts

packages/core/src/storage/docStore/KVDocumentStore.ts

packages/core/src/storage/docStore/SimpleDocumentStore.ts

packages/core/src/storage/graphStore/SimpleGraphStore.ts

packages/core/src/storage/graphStore/types.ts

packages/core/src/storage/indexStore/KVIndexStore.ts

packages/core/src/storage/indexStore/SimpleIndexStore.ts

packages/core/src/storage/indexStore/types.ts

packages/core/src/storage/kvStore/SimpleKVStore.ts

packages/core/src/storage/vectorStore/SimpleVectorStore.ts

pnpm-lock.yaml