Revisit and Improve /healthz Endpoint Logic

[rapidfix]

Problem Description

The /healthz endpoint in tee-worker currently uses a fixed window for error counting, resetting every 10 minutes. This leads to potential inaccuracies in health status reporting.

Acceptance Criteria

1. Replace the fixed window logic with a rolling window (e.g., last 10 minutes).
2. Ensure the /healthz endpoint correctly accumulates errors over the rolling window.
3. Document the new logic in the codebase.
4. Verify that the /readyz endpoint behaves as expected post-implementation.

Relevant Code References

• Fixed window logic: health.go#L26
• Error count reset: health.go#L51

Additional Notes

• This issue overlaps with the /readyz endpoint's behavior. Clarify if the same logic applies to both endpoints.
• Consider revisiting the overall healthcheck architecture for simplicity and reliability.