Added package name & version to HTTP headers

[huzaifa-d]

Summary of the pull request

This adds the package name and version to all HTTP request headers, in the form of UserAgent, sent to Dev Box APIs. This will facilitate easier telemetry for them.

Validation steps performed

Verified with the Dev Box team to make sure the requests received now had a distinct header.

PR checklist

• Closes The Azure extension should be using a Dev Home specific header when using the Dev Box rest APIs so telemetry is captured correctly #197
• Tests added/passed
• Documentation updated

[bbonaby]

Quick question, do you happen to know if Package.Current.Id.Name has whether its canary/dev in the name?

[huzaifa-d]

Quick question, do you happen to know if Package.Current.Id.Name has whether its canary/dev in the name?

@bbonaby I do, and it does, for example - Microsoft.Windows.DevHomeAzureExtension.Dev