community: callbacks guard_imports (#21173)

Issue: we have several helper functions to import third-party libraries
like import_uptrain in
[community.callbacks](https://api.python.langchain.com/en/latest/callbacks/langchain_community.callbacks.uptrain_callback.import_uptrain.html#langchain_community.callbacks.uptrain_callback.import_uptrain).
And we have core.utils.utils.guard_import that works exactly for this
purpose.
The import_<package> functions work inconsistently and rather be private
functions.
Change: replaced these functions with the guard_import function.

Related to #21133

libs/community/langchain_community/callbacks/wandb_callback.py

@@ -7,6 +7,7 @@ from typing import Any, Dict, List, Optional, Sequence, Union
 from langchain_core.agents import AgentAction, AgentFinish
 from langchain_core.callbacks import BaseCallbackHandler
 from langchain_core.outputs import LLMResult
+from langchain_core.utils import guard_import
 
 from langchain_community.callbacks.utils import (
     BaseMetadataCallbackHandler,
@@ -20,14 +21,7 @@ from langchain_community.callbacks.utils import (
 
 def import_wandb() -> Any:
     """Import the wandb python package and raise an error if it is not installed."""
-    try:
-        import wandb
-    except ImportError:
-        raise ImportError(
-            "To use the wandb callback manager you need to have the `wandb` python "
-            "package installed. Please install it with `pip install wandb`"
-        )
-    return wandb
+    return guard_import("wandb")
 
 
 def load_json_to_dict(json_path: Union[str, Path]) -> dict: