Paoxiaomooo sync mcp tool callback addmethod

[paoxiaomooo]

This PR introduces server name-based filtering capabilities to AsyncMcpToolCallbackProvider, matching the functionality already present in the synchronous implementation. The changes include:

​​New Constructor​​:
public AsyncMcpToolCallbackProvider(List mcpClients, Set allowedServerNames)

• Filters clients by allowed server names during initialization
• aintains existing asynchronous behavior
• Includes null/empty validation
  ​​New Reactive Utility Method​​:
  public static Flux asyncToolCallbacksByServer(List mcpClients, Set allowedServerNames)
• Provides end-to-end reactive pipeline for filtered tool discovery
• Performs duplicate tool name validation
• Preserves non-blocking characteristics

Why Add Server Filtering?

1. Selective Tool Discovery – Only fetch tools from specified servers, reducing overhead and improving performance.
2. Consistent API – Matches the sync version’s functionality, avoiding surprises.
3. Reactive Efficiency – Built-in non-blocking filtering for cleaner, optimized async flows.
4. Operational Control – Enables precise server management in multi-server environments.

Before: Manual filtering + duplicate checks.
After: Single-line reactive filtering with validation.
// Cleaner, safer usage
Flux tools = asyncToolCallbacksByServer(clients, allowedServers);