1.0.0-beta4 - Guided test workflow and honest gate figures.

Highlights since 1.0.0-beta3:
- A guided three-step test workflow with drafts, shared datasets, run
  comparison and recovery of interrupted runs (#3594748).
- Gate aggregates count only runs that carry gate evidence (#3594741).
- Import every_eval_ever envelopes from the results dashboard (#3594742).
- markdown_structure rubric checks now run (#3594743).
- Result pages no longer crash when the summary links a rubric or
  dataset (#3594750).

Upgrading: run drush updatedb (10038, 10039). File datasets are now
refused in full when invalid (#3594732). See CHANGELOG.md.