Agents v2 (branch-to-branch): fix/customize AzureAISearchAgentTool

[trrwilson]

Problem

After the original integration, AzureAISearchAgentTool added a resource property -- this wasn't customized for pattern or naming consistency and the AgentTool.CreateAzureAISearchTool() factory method wasn't updated to match, instead using a now-internal, deserialization-only constructor that didn't set a value for this required resource property.

Fixes

• Renamed the new "resource" to AzureAISearchToolOptions for naming/pattern consistency
  • Renamed consumed type for index to AzureAISearchIndex
• Made both parameterless and parameterized constructors for the tool work as intended (empty options for parameterless)
• Updated tool factory method to accept the now-renamed options type
• Updated smoke test coverage to exercise this specific tool/data