[storage-blob] environment variable inputs and samples with error handling

[YoDaMa]

Environment Variables in Samples

This one is simple. Rather than having users edit and paste in their Account and Account Key, pass them in as environment variables. This is easy to do when debugging using VSCode, and also takes minimal effort through the command prompt. The benefit is that users will be less likely to publish personal information in files.

Samples with Error Handling

In the samples for azure storage v12 I don't see any sample dealing with how to handle an HTTP error (for example 400). Can error handling be added to the advanced.js sample?

[XiaoningLiu]

@HarshaNalluru Do you have time for sample update about error handling in track2?

[jeremymeng]

Closing as the work is merged.