[Feat] Expose/allow configuration of github.copilot.chat.virtualTools.threshold in Eclipse Copilot

The Copilot chat integration currently fails when the virtual tool budget exceeds the default threshold, throwing:

“You may not include more than 128 tools in your request.”

This seems to be controlled by the internal setting github.copilot.chat.virtualTools.threshold, which is available in VS Code but not exposed in the Eclipse Copilot experience.

Problem:
• In large agent/chat sessions, the number of virtual tools can exceed the default limit.
• There is no visible way in Eclipse to lower or tune the threshold.
• This makes Copilot unusable in larger workspaces or when many tools are available.

Expected behavior:
• Allow users to configure github.copilot.chat.virtualTools.threshold from Eclipse preferences or a supported config mechanism.
• Or expose a simpler user-facing setting such as “Maximum virtual tools / tool budget.”
• Ideally, this should be adjustable without requiring undocumented internal settings.

Use case:
• Large projects with many tools or context providers.
• Users working in Eclipse who need to keep Copilot requests under the hard limit without being blocked by a fixed internal threshold.

Additional notes:
• The setting appears to be hidden/internal and not discoverable in the Eclipse UI.
• Having a supported configuration path would make the behavior predictable and reduce failures in real-world large-workspace usage.

Start at the Eclipse preferences integration and trace how github.copilot.chat.virtualTools.threshold is handled in the Copilot chat experience. Define whether the existing setting or a user-facing tool-budget option should be exposed, then verify that the configured value is discoverable and prevents the reported tool-limit failure.