feat(CategoryTheory): characterize pullback squares via the Over category

[michaellee94]

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[github-actions]

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[github-actions]

PR summary 3a4b36f227

Import changes exceeding 2%

%	File
+34.29%	Mathlib.CategoryTheory.Comma.Over.Pullback

Import changes for modified files

Dependency changes

File	Base Count	Head Count	Change
Mathlib.CategoryTheory.Comma.Over.Pullback	455	611	+156 (+34.29%)

Import changes for all files

Files	Import difference
Mathlib.CategoryTheory.Abelian.Preradical.Basic	1
3 files Mathlib.CategoryTheory.Monoidal.Closed.Ideal Mathlib.CategoryTheory.Subobject.MonoOver Mathlib.CategoryTheory.Subterminal	3
4 files Mathlib.CategoryTheory.LocallyCartesianClosed.ChosenPullbacksAlong Mathlib.CategoryTheory.LocallyCartesianClosed.ExponentiableMorphism Mathlib.CategoryTheory.LocallyCartesianClosed.Over Mathlib.CategoryTheory.LocallyCartesianClosed.Sections	4
Mathlib.CategoryTheory.Comma.Over.Pullback	156

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Declarations diff

+ isoOverPullback
+ ofIsoOverPullback
+ overPullback_iff

You can run this locally as follows

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

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

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

---

No changes to technical debt.

You can run this locally as

./scripts/reporting/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).

[michaellee94]

+34.29% Mathlib.CategoryTheory.Comma.Over.Pullback

Would it be better for this to go somewhere else?