Add validation to block publishing of invalid extension type packages

[anthony-c-martin]

If you make a mistake with authoring a types package (for example, using foo@1 rather thanfoo@v1 for a resource type name, the publishing is permitted, but then the consumption fails with a cryptic error:

The referenced extension types artifact has been published with malformed content

There's nothing really actionable we can show to the consumer, so we need to add more guard rails to ensure we don't allow an invalid package to be published.