Update ADK doc according to issue #1113 - 3 - EnterpriseWebSearchTool for Vertex AI Search

[adk-bot]

Suggestion #3: Clarification on Search Tools

The EnterpriseWebSearchTool is for Vertex AI Search, which is different from Google Search grounding (google_search tool). The documentation can be confusing.

Proposed Change:
Add a new document or a section in the tools documentation to clarify the differences between the various search tools available in ADK.

Current state:
The documentation primarily focuses on Google Search grounding and does not clearly differentiate it from other search offerings.

Proposed Change:
Create a new page or section that explains:

• Google Search grounding (google_search tool): For Gemini models.
• Enterprise Web Search (EnterpriseWebSearchTool): For Vertex AI Search.
• How to choose the right tool for their use case.

Reasoning:
The distinction between the different search tools is not clear in the current documentation, which can lead to confusion.

Reference:

• src/google/adk/tools/enterprise_search_tool.py