Create the Spring AI Ollama and OpenAI APIs with their builders

Spring AI 1.0 removed the convenience constructors of OllamaApi, OpenAiApi, OpenAiImageApi and OpenAiAudioApi. This replaces new OllamaApi() and new OllamaApi(baseUrl) with OllamaApi.builder().build() and OllamaApi.builder().baseUrl(baseUrl).build(), and new OpenAiApi(apiKey) and new OpenAiApi(baseUrl, apiKey) with OpenAiApi.builder().apiKey(apiKey).build() and OpenAiApi.builder().baseUrl(baseUrl).apiKey(apiKey).build(), and likewise for the image and audio APIs. Constructors taking more arguments are left for review.