Genie agent metadata

[manfredcalvo]

In this pull request, I am making the following changes to the GenieAgent:

1. Creating a Python class that extends the RunnableLambda interface to create the GenieAgent instead of having a function to represent the GenieAgent.
2. Adding a new boolean parameter to the GenieAgent class called "return_metadata." If the flag is True, then the output of the invoke function of the GenieAgent will have two keys: "messages" and "metadata." This metadata contains the direct response from GenieAPI, which is the object GenieResponse.
3. Some minor refactoring of the GenieAgent unit tests.

If the following screenshots, you can see the output dict and the output trace in both scenarios (return_metadata True and False)

When return_medata is False (this is the default value)

When return_metadata is True

[FMurray]

Suggestion: add a docstring

[manfredcalvo]

@FMurray Doc string added to the class.

[manfredcalvo]

@bbqiu, let me know if this can be merged or if I need to follow a different process.