[AUR-431, AUR-435] Add Agent Interface and ReWOO Agent implementation (#31)

* add base Tool

* minor update test_tool

* update test dependency

* update test dependency

* Fix namespace conflict

* update test

* add base Agent Interface, add ReWoo Agent

* minor update

* update test

* fix typo

* remove unneeded print

* update rewoo agent

---------

Co-authored-by: trducng <trungduc1992@gmail.com>

knowledgehub/pipelines/agents/utils.py

@@ -0,0 +1,22 @@
+from .base import AgentOutput
+
+
+def get_plugin_response_content(output) -> str:
+    """
+    Wrapper for AgentOutput content return
+    """
+    if isinstance(output, AgentOutput):
+        return output.output
+    else:
+        return str(output)
+
+
+def calculate_cost(model_name: str, prompt_token: int, completion_token: int) -> float:
+    """
+    Calculate the cost of a prompt and completion.
+
+    Returns:
+        float: Cost of the provided model name with provided token information
+    """
+    # TODO: to be implemented
+    return 0.0