Allow Set-DotNetVersions script to read from config.json for .NET releases

[lbussell]

Describe the Problem

Manually looking up the product versions to release and typing them in/copying them to the commandline takes time and is error-prone.

Describe the Solution

The .NET Release staging pipeline outputs a file called config.json that contains the .NET versions in the build. It looks like this:

{
  "Channel": "8.0",
  "Release": "8.0.3",
  "Runtime": "8.0.3",
  "Asp": "8.0.3",
  "Sdks": [
    "8.0.202",
    "8.0.103"
  ],
  ...
  "Runtime_Build": "8.0.3-servicing.24114.23",
  "Asp_Build": "8.0.3-servicing.24116.15",
  "Sdk_Builds": [
    "8.0.202-servicing.24116.49",
    "8.0.103-servicing.24116.48"
  ],
  ...
}

We should be able to read from this file in order to set the correct .NET versions for a release.

Ideally, we could also connect directly to Azure DevOps. I would like to be able to give Set-DotNetVersions.ps1 a build number and have it update everything automatically.

[lbussell]

[Triage] This would be a good gradual step towards release automation and simplify the release process for .NET container images.

[lbussell]

Here's one way to get the config.json file using the az CLI -

PS> az pipelines runs artifact download --organization https://dev.azure.com/dnceng/ --project internal --run-id $buildId --path . --artifact-name drop

[lbussell]

I wrote a prototype script that accomplishes this (locally). It takes an AzDo build ID and calls Set-DotnetVersions.ps1:
https://gist.github.com/lbussell/4a1ee1e552e7db69fccbfd359e14984f#file-set-dotnetversionsfrombuild-ps1