A better error message describing general class of auth problems

[vlada-shubina]

Related to https://github.com/dotnet/sdk-container-builds/issues/314 and https://github.com/dotnet/sdk-container-builds/issues/418

Current error message is as following: /opt/azure_repos/home_dir_tgw_user/.nuget/packages/microsoft.net.build.containers/0.4.0/build/Microsoft.NET.Build.Containers.targets(195,5): error CONTAINER1013: Failed to push to the output registry: System.ApplicationException: CONTAINER1001: Failed to upload blob to POST****

Consider improving it and providing possible generic CTA.

A message like the following should be emitted instead:

• No credentials found for registry:

Unable to authenticate to registry <REGISTRYNAME>. No credentials were found locally - you may need to login to the registry using `docker login <REGISTRYNAME> -u <USERNAME> -p <PASSWORD>.`

• Credentials present, but incorrect when a Token was used:

Unable to authenticate to registry <REGISTRYNAME>. Credentials were found locally but were not accepted by the registry. Check the permissions for the Bearer token associated with the registry.

• Credentials present, but incorrect when a Basic (username/password) was used:

Unable to authenticate to registry <REGISTRYNAME>. Credentials were found locally but were not accepted by the registry. Check the permissions for the user <USERNAME> associated with the registry.

Potential questions:

• Is it ok to expose <USERNAME> in the message?
• Is it ok to try to find the sub claim in the Bearer token and emit it, since tokens are often tracked/inventoried by the 'subject' (user id) that they were created for?