Add Ollama embedding usage metadata

Current `OllamaApi` and the related `OllamaEmbeddingModel` do not use the [Ollama Embedding](https://github.com/ollama/ollama/blob/main/docs/api.md#generate-embeddings) metadata response fields such as: total_duration, load_duration and prompt_eval_count. Later can be used to compute the embedding usage metrics