New tests, documentation, and diagnostic data type/rank

New Features

• New intrinsic_array_t type and constructor facilitate intrinsic-array diagnostic data. 📑

Refactoring

• Reorganize/rename files/directories. 🧹

Testing

• All tests pass. 💯
• Add unit tests.
• Add tests that intentionally error-terminate.
• Silence most output from tests that intentionally error-terminate.

Documentation

• Update README.md. 📜
• Add PlantUML diagram for classes in Assert 🪴
• Fix typographical errors in documentation 🩹