Remove Resource and Deploy to simplify the model.
Previously, we differentiated between Resources and Artifacts, and SLSA was a property of a Resource's security policy. However, many readers found this concept very confusing. Now, SLSA is purely a property of the artifact. If provenance exists showing that it met the requirements, the artifact meets the level. No policy or notion of "resource" is required. This simplifies the model at some cost of security, which we have collectively decided is worth the trade-off. NOTE: The Vision section will be updated in a future change.