Use build number to replace git hash display on the UI

[Yicong-Huang]

We have been displaying git hash number on the UI to show the version information. However, git hash are bundled with source code version, not the build version. The implementation of displaying git hash was also hacky, which relies on the .git folder. In production, this .git folder are usually not in the deployment, nor should be in the deployment.

Thus, we should redesign this to show "build number" instead of "git hash" on the UI, to differentiate the service version. Libraries such as https://www.npmjs.com/package/build-number-generator can be used to achieve this purpose.

[chenlica]

Here's a screenshot of the current implementation, which is broken after we adopted the kubernetes-pod architecture:

[Ma77Ball]

/take