feat(Order/Basic): PartialOrder.ext_lt

[vihdzp]

Two partial / linear orders with the same < relation are the same.

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Note that this isn't true for preorders: two orders where ∀ x y, ¬ x < y could consist entirely of incomparable or entirely of order-equivalent elements.

[github-actions]

PR summary b7cb653afb

Import changes for modified files

No significant changes to the import graph

Import changes for all files

Files	Import difference

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Declarations diff

+ LinearOrder.ext_lt
+ PartialOrder.ext_lt

You can run this locally as follows

## summary with just the declaration names:
./scripts/declarations_diff.sh <optional_commit>

## more verbose report:
./scripts/declarations_diff.sh long <optional_commit>

The doc-module for script/declarations_diff.sh contains some details about this script.

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No changes to technical debt.

You can run this locally as

./scripts/technical-debt-metrics.sh pr_summary

• The relative value is the weighted sum of the differences with weight given by the inverse of the current value of the statistic.
• The absolute value is the relative value divided by the total sum of the inverses of the current values (i.e. the weighted average of the differences).