Fix TypeError in fin_quant coding step (#1224)

[utsab345]

This PR fixes the TypeError: data must be str, not dict issue reported in #1224. I modified the assign_code_list_to_evo function in factor_coder/evolving_strategy.py and model_coder/evolving_strategy.py to handle dictionary responses from the LLM. Tests in test_evolving_strategy_fix.py now pass.

@microsoft/rdagent-maintainers Please review.

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📚 Documentation preview 📚: https://RDAgent--1265.org.readthedocs.build/en/1265/

[utsab345]

Any reviews?? @you-n-g @chaosddp @corygehr

[utsab345]

@you-n-g @chaosddp @corygehr @cslwqxx ??

[SunsetWolf]

Hi, @utsab345
Thank you for your contribution to RD-Agent. There is more than just the TypeError issue fixed in this PR. There are also some changes based on pydantic version adaptation.

• The TypeError issue is fixed in PR 1279. So the changes have been duplicated here.
• The modification about pydantic can be kept as it adapts to the new version of pydantic.