program@v4.0.0

What's new

• Publish spl-single-pool v4.0.0 by @github-actions[bot]
• Use size_of() uniformly (#552) by @2501babe
• Use Rent over rent_exempt_reserve (#542) by @2501babe
• Test against 1sol minimum delegation (#502) by @2501babe
• Use multiple stake programs in tests (#497) by @2501babe
• Update program and cli to sdk 3.0 (#407) by @2501babe