Move grounding tool to reusable parent tools dir

[amrit110]

This pull request refactors the location and import paths for the Google Search grounding tool and its related utilities, moving them from the knowledge_agent module to a new, reusable tools package. This improves modularity and code organization, making these tools easier to reuse across different agents and tests. All relevant imports and test files have been updated to reflect this new structure.

Refactor and modularization of Google Search tool:

• Moved grounding_tool.py from aieng.agent_evals.knowledge_agent to aieng.agent_evals.tools as search.py, and updated its module docstring to reflect broader applicability.
• Added a new aieng.agent_evals.tools package with an __init__.py that exposes GroundedResponse, GroundingChunk, create_google_search_tool, and format_response_with_citations for easy import.

Import and usage updates:

• Updated all imports in source and test files to use the new aieng.agent_evals.tools path instead of the old knowledge_agent.grounding_tool path. [1] [2] [3] [4] [5] [6] [7]

Test organization:

• Renamed and moved the test file for the grounding tool to tests/aieng/agent_evals/tools/test_search.py to match the new module location and updated test docstrings accordingly.
• Added an empty docstring to tests/aieng/agent_evals/tools/__init__.py to initialize the test package.

[fcogidi]

LGTM