Cannot add multiple MCP servers to agent

- **Package Name**: azure-ai-agents
- **Package Version**: 1.2.0b2
- **Operating System**: Windows
- **Python Version**: 3.11.9

**Describe the bug**
Can not connect to multiple MCP servers. According the document, https://learn.microsoft.com/en-us/azure/ai-foundry/agents/how-to/tools/model-context-protocol?utm_source=chatgpt.com, multiple MCP servers can be supported for an agent. But when create two McpTool objects with two different MCP server information and call ToolSet.add(), exception will be thrown.

**To Reproduce**
Below is the sample codes causing exception.

mcp_toolset = ToolSet()
mcp_tool1 = McpTool(server_label="label1",server_url="url1")
mcp_toolset.add(mcp_tool1)
mcp_tool2 = McpTool(server_label="label2",server_url="url2")
mcp_toolset.add(mcp_tool2) ------> Here exception will be thrown that not allow two tools with same type added to ToolSet(). Below is the exception information.

raise ValueError("Tool of type {type(tool).__name__} already exists in the ToolSet.")
ValueError: Tool of type {type(tool).__name__} already exists in the ToolSet.

**Expected behavior**
Multiple MCP servers should be configured with agent successfully

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**Additional context**
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