Implement Caller-Specified Response Delay in Yardstick #64
Description
We want to run performance tests through the ToolHive proxy. However, because Yardstick simply echoes back a response, there are no external network calls, resulting in the fastest possible response times. To better simulate real-world conditions, we should add a configurable delay mechanism that callers can specify and that Yardstick will honour by waiting a defined amount of time before responding. This would more accurately model a production MCP server, which may take several seconds to return a response.