feat(CategoryTheory/SmallObject): promote a construction from Over to Arrow

[joelriou]

With this change, in the proof of the small object arguments (#20245), we shall get a functorial factorization instance HasFunctorialFactorization instead of HasFactorization.

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• depends on: chore(CategoryTheory): make relevant parameters explicit in Arrow.homMk. #20259

[github-actions]

PR summary 73465c244d

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

No declarations were harmed in the making of this PR! 🐙

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).

[mathlib4-dependent-issues-bot]

This PR/issue depends on:

• chore(CategoryTheory): make relevant parameters explicit in Arrow.homMk. #20259
  By Dependent Issues (🤖). Happy coding!