fix: prefer using embedding model from vector store (#1708)

packages/llamaindex/src/llm/openai.ts

packages/llamaindex/tests/MetadataExtractors.test.ts

packages/llamaindex/tests/Selectors.test.ts

packages/llamaindex/tests/indices/SummaryIndex.test.ts

packages/llamaindex/tests/indices/VectorStoreIndex.test.ts

packages/llamaindex/tests/utility/mockOpenAI.ts

packages/llamaindex/tests/utility/mockStorageContext.ts

packages/providers/deepseek/package.json

packages/providers/deepseek/src/index.ts

packages/providers/deepseek/src/llm.ts

packages/providers/deepseek/tsconfig.json

packages/providers/fireworks/package.json

packages/providers/fireworks/src/embedding.ts

packages/providers/fireworks/src/index.ts

packages/providers/fireworks/src/llm.ts

packages/providers/fireworks/tsconfig.json

packages/providers/jinaai/package.json

packages/providers/jinaai/src/embedding.ts

packages/providers/jinaai/src/index.ts

packages/providers/jinaai/tsconfig.json