Add Ollama provider with response schema support & create LLM provider directory

[itsmvd]

This pull request introduces the following changes:

• Implements response schema support for Ollama provider: Add response_schema support to ollama.py (already added to the interface). This allows for structured data extraction from the LLM. This functionality is currently used for the experimental llm_summarize feature.
• Refactors LLM provider directory: Moves all LLM providers to new timesketch/lib/llms/providers directory for better organization.