Write configs as part of conversion pass

[shaahji]

Write configs as part of conversion pass

For generative models using GenAI model builder, when using ONNX model as input configs (config.json, generation_config.json & tokenizer) are required inputs. So, write out these files as outputs from the conversion pass.

Checklist before requesting a review

• Add unit tests for this change.
• Make sure all tests can pass.
• Update documents if necessary.
• Lint and apply fixes to your code by running lintrunner -a
• Is this a user-facing change? If yes, give a description of this change to be included in the release notes.
• Is this PR including examples changes? If yes, please remember to update example documentation in a follow-up PR.

(Optional) Issue link

[jambayk]

Can you abstract some of the common code like file -> parent_dir in the follow up PR?