Add context parameter to TCP/UDP stream health checks and client constructors
for proper cancellation and deadline propagation. Switch from encoding/json
to sonic for faster JSON unmarshaling.
Standardize HTTP client timeouts to 5 seconds
across agent pool and health check.
- Correct BaseContext nil check in Context() method
- Move NewMonitor from monitor.go to new.go
- Export ErrDockerHealthCheckFailedTooManyTimes and add ErrDockerHealthCheckNotAvailable
- Return ErrDockerHealthCheckNotAvailable when container has no health check configured
- Only log first docker health check failure and skip logging for ErrDockerHealthCheckNotAvailable
- Use mon.Context() instead of mon.task.Context() to avoid nil panic
