improve import seeding

[Josh-XT]

This pull request includes several changes to the agixt/SeedImports.py file to improve the import process for agents, extensions, chains, prompts, and providers. The changes include adding checks to prevent duplicate entries, ensuring a default user exists, and refactoring the code for better readability and maintainability.

Improvements to import processes:

• Added a new function ensure_default_user to ensure the default admin user exists.
• Modified import_agents, import_extensions, import_chains, import_prompts, and import_providers functions to include checks for existing entries before adding new ones to prevent duplicates. [1] [2] [3] [4] [5]

Codebase simplification and refactoring:

• Removed unused imports and code related to conversations to clean up the file. [1] [2]
• Refactored the retry logic in import_chains to make it more concise and readable.
• Ensured that sessions are properly closed after database operations to avoid potential resource leaks. [1] [2] [3] [4]