Add Primitive repository APIs (`ResourceRepository`, `ToolsRepository`, ... )

Currently, McpStatelessAsyncServer and McpAsyncServer save resources, tools, prompts, and completionswithCopyOnWriteArrayList`.

https://github.com/modelcontextprotocol/java-sdk/blob/main/mcp-core/src/main/java/io/modelcontextprotocol/server/McpStatelessAsyncServer.java#L60-L68

I want to provide an API (for example, ResourcesRepository) that, by default, uses the current in-memory strategy but can be replaced, for example, by a dynamic implementation that returns a different list of resources depending on the currently authenticated user.

从 McpStatelessAsyncServer.java 和 McpAsyncServer.java 开始，尤其关注 issue 中引用的 CopyOnWriteArrayList 字段，并追踪资源、工具、提示和补全的存储与提供方式。定义 repository API 边界，同时保留当前的内存中行为并允许依赖用户的实现；完成标准是四个原始集合都使用可替换的 API，且不改变现有的服务器行为。