`EvaluationResult.feedback_config` silently drops unknown or partial dict fields without error

### Checked other resources - [x] I added a very descriptive title to this issue. - [x] I used the GitHub search to find a similar question and didn't find it. - [x] I am sure that this is a bug in LangChain rather than my code. - [x] The bug is not resolved by updating to the latest stable version of LangChain (or the specific integration package). - [x] I posted a self-contained, minimal, reproducible example. A maintainer can copy it and run it AS IS. ### Example Code ```python from langchain_core.tracers.evaluation import EvaluationResult result = EvaluationResult( key="sentiment", value="positive", feedback_config={"threshold": 1.0} ) print(result.feedback_config) ``` ### Error Message and Stack Trace (if applicable) {} ### Description When passing a dict to `EvaluationResult.feedback_config`, the data is silently discarded. This causes unexpected behavior and makes it impossible to store arbitrary dict configurations directly, despite the type hint allowing `dict`. ### System Info System Information ------------------ > OS: Linux > OS Version: #148-Ubuntu SMP Fri Mar 14 19:05:48 UTC 2025 > Python Version: 3.10.16 (main, Dec 11 2024, 16:24:50) [GCC 11.2.0] Package Information ------------------- > langchain_core: 0.3.65 > langchain: 0.3.25 > langchain_community: 0.3.25 > langsmith: 0.3.45 > langchain_anthropic: 0.3.1 > langchain_aws: 0.2.2 > langchain_chroma: 0.2.0 > langchain_cohere: 0.3.5 > langchain_experimental: 0.3.2 > langchain_fireworks: 0.2.6 > langchain_google_vertexai: 2.0.5 > langchain_groq: 0.2.2 > langchain_mistralai: 0.2.4 > langchain_openai: 0.2.14 > langchain_text_splitters: 0.3.8 > langchain_together: 0.2.0 > langchain_unstructured: 0.1.5 > langgraph_sdk: 0.1.34 Optional packages not installed ------------------------------- > langserve Other Dependencies ------------------ > aiohttp: 3.12.12 > aiohttp<4.0.0,>=3.8.3: Installed. No version info available. > anthropic: 0.40.0 > anthropic[vertexai]: Installed. No version info ava…