Description:

• The .NET CDN URLs are changing. This PR updates actions/setup-dotnet@v1 to use the new URLs where needed.
• This PR also updates the action to use the the latest install-dotnet scripts which account for the new URLs. Note that these were pulled from the latest commit in https://github.com/dotnet/install-scripts as the new install scripts are not yet live on the https://dot.net/ website yet.

Related issue:
Add link to the related issue.

Check list:

• Mark if documentation changes are required.
• Mark if tests were added or updated to cover the changes.