Feature/telemetry usage endpoint

[sametd]

This PR enhances the telemetry service and introduces new features, including:

• New /metrics Endpoint: Displays usage statistics for better monitoring.
• Helper Functions for Handlers: Simplifies code and improves reusability.
• Consistent Logging: Uvicorn logs now follow the Polytope logging format.
• Separate Metrics Task for Garbage Collector: Improves task organization.
• Retention of Processed Metrics: Processed metrics are kept by default, even when requests are removed.
• API Key Obfuscation: Enhances security by hiding API keys in logs and metrics.
• User ID in Metrics: Adds user ID to metrics for better tracking.
• Improved Store Initialisation: Garbage collector now initialises the request and metric stores together.

[peshence]

Couple of very minor comments, it looks great! Especially appreciate the little things like not repeating the shared portion of the path