Misc improvements and fixes

[jlamypoirier]

✨ Description

Some misc stuff ectracted from #245 to reduce its size.

• Replace flaky and poorly formatted __repr__ from dataclass with a formatted config (to_logs)
• Remove the ignored default_factory for nested config fields.
• Make instantiation consistent by forcing it to go through _from_dict.
• Rename model_config_class -> model in ConvertConfig
• Add some type hints and standardize @config_class to help static type checkers.
• Various fixes and minor improvements

🔍 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)

[tscholak]

LGTM

[tscholak]

I haven't checked the new type annotations with vscode yet, will report back if there are still problems. thanks!