Litellm replace in knowledge base

[ea-rus]

Description

Updates:

Replaced litellm module by custom code to access to bedrock, gemini, snowflake providers

Affected functions:

• Emedding (bedrock, gemini, snowflake are called using custom clients)
• Reranking
  • list of providers are restricted to: openai, azure, ollama, bedrock, gemini, snowflake
• LLM function, of providers are restricted to: openai, azure, ollama, bedrock, gemini, snowflake
  • but you can't choose snowflake in GUI
  • the other providers won't work: nvidia_nim, anthropic, writer

Fixes https://linear.app/mindsdb/issue/FQE-2200/removereplace-litellm

Type of change

• ⚡ New feature (non-breaking change which adds functionality)
• 📢 Breaking change (fix or feature that would cause existing functionality not to work as expected)

Verification Process

To ensure the changes are working as expected:

• Test Location: Specify the URL or path for testing.
• Verification Steps: Outline the steps or queries needed to validate the change. Include any data, configurations, or actions required to reproduce or see the new functionality.

Additional Media:

• I have attached a brief loom video or screenshots showcasing the new functionality or change.

Checklist:

• My code follows the style guidelines(PEP 8) of MindsDB.
• I have appropriately commented on my code, especially in complex areas.
• Necessary documentation updates are either made or tracked in issues.
• Relevant unit and integration tests are updated or added.