Add backwards-compatibility checking for AlgebraicTypeLayouts used in system tables

[kazimuth]

Description of Changes

Add backwards-compatibility checking for AlgebraicTypeLayouts used in system tables. This required implementing backwards-compatibility validation logic for BSATN and BFLATN. I still need to add an actual serialization test for BFLATN but I'm still figuring out the plumbing there.

This doesn't need to happen until post-1.0.

API and ABI breaking changes

None

Expected complexity level and risk

0

Testing

Added proptests and some manual tests, but it isn't airtight yet.

[CLAassistant]

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