Allow dynamic generation of tool definition in MCP Server

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Expected Behavior
Add a boolean property/flag called "callGetToolCallbacksEverytime".
If the flag is set to true then everytime an MCP server receives a tools/list request, the MCP server should call getToolCallbacks on registered ToolCallbackProvider. This will allow an MCP Server's implementation to dynamically generate ToolDefinition based on the request. All the implementation will need to do is provide a custom ToolCallbackProvider and also set the flag to true. If the flag is set to "false" then the current behaviour of calling getToolCallbacks only during startup is used.

Current Behavior

In the current behavior, i configured a custom ToolCallbackProvider to override the "description" that is generated for my tool. However, my tool callback provider's "getToolCallbacks" method is only called once during application startup. When my MCP Client sends a "tools/list" request, the MCP Server returns the tool definitions it computed at application startup. It doesn't try to get the new list from ToolCallbackProvider.

In the current behavior, getToolCallbacks is called on a ToolCallbackProvider only at startup. This makes it impossible to generate tool definition dynamically i.e. when "tools/list" request is received.

Context

My use case requires me to generate tool description dynamically based on the user of the MCP Client. MCP Client invokes a "tools/list" request but my Spring AI based MCP Server returns tooldefinition that it computed at the application startup. In my use case i would like to generate description for my tool dynamically everytime the MCP Server receives a "tools/list" request.

先追蹤啟動期間呼叫 ToolCallbackProvider.getToolCallbacks 的位置，以及 MCP 伺服器處理 tools/list 請求的位置。新增要求的 flag，讓 tools/list 可以在快取的 callback 與再次取得這些 callback 之間選擇，然後使用現有的伺服器測試驗證 flag 的兩種設定和動態工具定義。