[ Refactored ] embedding models and [ Update ] documentation for Gemini model

[parshvadaftari]

Description

Refactored and updated embedding models in gemini.py, huggingface.py, and ollama.py. Added documentation for the Gemini embedding model in gemini.mdx.

Fixes #xxxx

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Refactor (does not change functionality, e.g. code style improvements, linting)
• Documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

Please delete options that are not relevant.

• Unit Test
• Test Script

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules
• I have checked my code and corrected any misspellings

Maintainer Checklist

• closes #xxxx
• Made sure Checks passed

[Dev-Khant]

Thanks for the contribution @parshvadaftari