Feature: telemetry module & important events recording

[powerfooI]

Summary

1. Encapsulate record.EventRecorder interface in k8s client-go package, upload telemetry data alongside operator manager create event.
2. A throttler which hold a buffered channel and a group of workers who fetch uploading data in infinite loop.
3. A metrics puller which extract informations from the host environment
4. A flexible asynchronous method to generate telemetry record and send to the buffered channel of throttler
5. Disable or debug the module with environment variables
6. All functions pass bundled unit tests

[chris-sun-star]

use telemetry as Recorder

[chris-sun-star]

LGTM

[powerfooI]

Add event recordings for important transitions. #38