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/comet_ml_callback.py

@@ -6,6 +6,7 @@ from typing import Any, Callable, Dict, List, Optional, Sequence
 from langchain_core.agents import AgentAction, AgentFinish
 from langchain_core.callbacks import BaseCallbackHandler
 from langchain_core.outputs import Generation, LLMResult
+from langchain_core.utils import guard_import
 
 import langchain_community
 from langchain_community.callbacks.utils import (
@@ -21,15 +22,7 @@ LANGCHAIN_MODEL_NAME = "langchain-model"
 
 def import_comet_ml() -> Any:
     """Import comet_ml and raise an error if it is not installed."""
-    try:
-        import comet_ml
-    except ImportError:
-        raise ImportError(
-            "To use the comet_ml callback manager you need to have the "
-            "`comet_ml` python package installed. Please install it with"
-            " `pip install comet_ml`"
-        )
-    return comet_ml
+    return guard_import("comet_ml")
 
 
 def _get_experiment(