community: Update Replicate LLM and fix tests (#27655)

**Description:** 
- Fix bug in Replicate LLM class, where it was looking for parameter
names in a place where they no longer exist in pydantic 2, resulting in
the "Field required" validation error described in the issue.
- Fix Replicate LLM integration tests to:
  - Use active models on Replicate.
- Use the correct model parameter `max_new_tokens` as shown in the
[Replicate
docs](https://replicate.com/docs/guides/language-models/how-to-use#minimum-and-maximum-new-tokens).
  - Use callbacks instead of deprecated callback_manager.

**Issue:** #26937 

**Dependencies:** n/a

**Twitter handle:** n/a

---------

Signed-off-by: Fayvor Love <fayvor@gmail.com>
Co-authored-by: Chester Curme <chester.curme@gmail.com>

libs/community/langchain_community/llms/replicate.py

@@ -78,7 +78,7 @@ class Replicate(LLM):
     @classmethod
     def build_extra(cls, values: Dict[str, Any]) -> Any:
         """Build extra kwargs from additional params that were passed in."""
-        all_required_field_names = {field.alias for field in get_fields(cls).values()}
+        all_required_field_names = {field for field in get_fields(cls).keys()}
 
         input = values.pop("input", {})
         if input: