Handle nullable output values marked as non-nullable in the schema

[myhau]

Ideas:

• laziness (like in Besom)
• default values (e.g. for String map it to "")
• print error message with issue description and repository to raise it in

[jplewa]

I reported this type of an issue in GCP ages ago and nothing so far: https://github.com/pulumi/pulumi-gcp/issues/1125