e2e testing for provenance-only workflow

[ianlewis]

Related #76

e2e tests:

• Different triggers (push, workflow_dispatch, schedule, new-tag)
  • push, schedule
    • Fix prov-only e2e tests and permissions example-package#27
    • Add schedule and push e2e test for provenance-only workflow example-package#24
  • workflow_dispatch
    • Add generic workflow_dispatch e2e test example-package#41
  • tag
    • Add tag e2e test for generic workflow example-package#33
• Different branches (for each trigger above)
  • Add branch tests for generic workflow example-package#50
• Pre-submit e2e tests
  • Add pre-submit test workflow for provenance-only workflow #122
• Different arguments: vary the env variables, make sure the final provenance contains the right information
  • Refactor authenticity check example-package#58
• Builder information, such as runner env (except hash)

General Tasks:

• Auto-close issues when e2e tests pass
• Update documentation as necessary

[ianlewis]

e2e tests for the generic workflow have good coverage for now. Will add new ones as we add new features.