Add nomic embedding model provider

[yaoice]

Checklist:

Important

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• Please open an issue before creating a PR or link to an existing issue
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Description

Fixes #8638

Add nomic embedding model provider to support，Nomic Embed's Surprisingly Good MTEB Arena Elo Score. reference：https://www.nomic.ai/blog/posts/evaluating-embedding-models

Nomic Embedding Introduce：https://atlas.nomic.ai/
Nomic Text Embedding Model List：https://docs.nomic.ai/atlas/models/text-embedding
Nomic Embedding python sdk reference：https://docs.nomic.ai/reference/python-api/embeddings

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update, included: Dify Document
• Improvement, including but not limited to code refactoring, performance optimization, and UI/UX improvement
• Dependency upgrade

Testing Instructions

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