Spring-ai Tidy up project directory structure

The generative AI client implementations are modules sitting at the top of the project, e.g. spring-ai-ollama. Create a directory, generative-clients and put the various client modules in that directory

Comment From: Sohardh

@markpollack was going to pick this up, just wanted to confirm, i am shifting the following modules to generative-clients

• spring-ai-azure-openai
• spring-ai-huggingface
• spring-ai-ollama
• spring-ai-openai
• spring-ai-vertex-ai

Comment From: markpollack

We have gone with this package structure. Please comment if you have suggestions. Closing the issue for now.

├── models
│   ├── spring-ai-azure-openai
│   ├── spring-ai-bedrock
│   ├── spring-ai-huggingface
│   ├── spring-ai-ollama
│   ├── spring-ai-openai
│   ├── spring-ai-postgresml
│   ├── spring-ai-transformers
│   └── spring-ai-vertex-ai