langchain-community[major]: Upgrade community to pydantic 2 (#26011)

This PR upgrades langchain-community to pydantic 2.


* Most of this PR was auto-generated using code mods with gritql
(https://github.com/eyurtsev/migrate-pydantic/tree/main)
* Subsequently, some code was fixed manually due to accommodate
differences between pydantic 1 and 2

Breaking Changes:

- Use TEXTEMBED_API_KEY and TEXTEMBEB_API_URL for env variables for text
embed integrations:
cbea780492

Other changes:

- Added pydantic_settings as a required dependency for community. This
may be removed if we have enough time to convert the dependency into an
optional one.

---------

Co-authored-by: Eugene Yurtsev <eyurtsev@gmail.com>
Co-authored-by: Bagatur <baskaryan@gmail.com>

libs/community/langchain_community/llms/mosaicml.py

@@ -4,6 +4,7 @@ import requests
 from langchain_core.callbacks import CallbackManagerForLLMRun
 from langchain_core.language_models.llms import LLM
 from langchain_core.utils import get_from_dict_or_env, pre_init
+from pydantic import ConfigDict
 
 from langchain_community.llms.utils import enforce_stop_tokens
 
@@ -58,8 +59,9 @@ class MosaicML(LLM):
 
     mosaicml_api_token: Optional[str] = None
 
-    class Config:
-        extra = "forbid"
+    model_config = ConfigDict(
+        extra="forbid",
+    )
 
     @pre_init
     def validate_environment(cls, values: Dict) -> Dict: