Fix invalid level data order and padding

[donmccurdy]

Changes:

• fixes order of level data (vs. level index)
• fixes level data padding
• adds validation test suite
• adds utilities for calculating block dimensions, block byte length, etc.
• fixes #117

Remaining:

• [x] clean up block size calculation
• [x] add pre-version macro for validation
• [x] major version

[donmccurdy]

• #120 👈
• main

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[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 98.26%. Comparing base (1344d3a) to head (8a4641d).

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #120 +/- ## ========================================== + Coverage 97.45% 98.26% +0.81% ========================================== Files 7 7 Lines 981 1439 +458 Branches 48 54 +6 ========================================== + Hits 956 1414 +458 Misses 25 25 ```

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