Qwen2 converter

[bigximik]

✨ Description

Implements the dense Qwen2 checkpoint converter according to
Hugging Face Transformers Qwen2.

The use_sliding_window, sliding_window, and max_window_layers parameters from the HF Qwen2 configuration are ignored during conversion, as they are not part of the architecture parameters. This is the same way the sliding_window parameter is handled in the Mistral checkpoint converter.

part of the #135

🔍 Type of change

Select all that apply:

• 🐛 Bug fix (non-breaking change that addresses a specific issue)
• 🚀 New feature (non-breaking change that adds functionality)
• ⚠️ Breaking change (a change that could affect existing functionality)
• 📈 Performance improvement/optimization (improves speed, memory usage, or efficiency)
• 🛠️ Code refactor (non-functional changes that improve code readability, structure, etc.)
• 📦 Dependency bump (updates dependencies, including Dockerfile or package changes)
• 📝 Documentation change (updates documentation, including new content or typo fixes)
• 🔧 Infrastructure/Build change (affects build process, CI/CD, or dependencies)

📝 Changes

List the key changes introduced in this PR:

1. Implements dense Qwen2 converter

✅ Checklist

Make sure the following tasks are completed before submitting the PR:

General

• 📜 I have read and followed the contributing guidelines.
• 🏷️ I am using a clear and descriptive PR title that summarizes the key change or feature introduced.
• 🎉 The functionality is complete, and I have tested the changes.
• 📝 I have updated the documentation if needed. (not applicable)
• ⚠️ The change does not introduce any new issues (e.g., runtime warnings, type checker errors, linting problems, unhandled edge cases).
• 🧩 I have commented my code, especially in hard-to-understand areas.

Dependencies and Configuration

• 🐋 I have updated the Docker configuration or dependencies, if applicable. (not applicable)
• 🔄 I have ensured compatibility with the existing setup after dependency changes. (not applicable)

Testing

• 🧪 I have added or updated tests to cover my changes.
• ✔️ New and existing tests pass locally with my changes. (tested affected llama starcder2 and qwen2 conversion)
• 🚦 I have tested these changes on GPUs and verified training stability.
• 🏋️ I have tested the changes on realistic training workloads, if applicable.

Performance Impact (not applicable)

[tscholak]

Great work, @bigximik!
I think next in line is #166, wdyt?

[tscholak]

@bigximik this is fine, but can you please add a todo here that says that this is a temporary hack until we can load these params from the config?