[Merged by Bors] - refactor(Algebra/Polynomial/Splits): continue deprecation

[tb65536]

This PR continues the deprecation in Splits.lean as we move over to the new API in Factors.lean.

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[github-actions]

PR summary 633ee94e38

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

+ Splits.comp_of_degree_le_one_of_invertible
+ Splits.comp_of_degree_le_one_of_monic
+ Splits.comp_of_natDegree_le_one
+ Splits.comp_of_natDegree_le_one_of_invertible
+ Splits.comp_of_natDegree_le_one_of_monic
+ Splits.splits_of_dvd
+ _root_.IsUnit.splits
+ splits_iff_comp_splits_of_natDegree_eq_one
+ splits_of_degree_le_one_of_invertible
+ splits_of_degree_le_one_of_monic
+ splits_of_natDegree_le_one_of_invertible
+ splits_of_natDegree_le_one_of_monic

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-merge-conflict-bot]

This pull request has conflicts, please merge master and resolve them.

[Vierkantor]

Otherwise I really like the results of this PR, code becomes quite a bit nicer! 🎉

[Vierkantor]

(Sorry for catching this only now!) Seeing the name Splits.of_dvd repeated so many times has made me realize I don't like it very much. I think it's because there are three parts of this lemma, a Splits input, a Dvd input, and a Splits output, and the name only mentions two of them? So there's a bit of a weird overlap in reading in having to assign the Splits to both in- and output.

Maybe Splits.splits_of_dvd or Splits.left_of_dvd? (Dvd.splits might also work, although it's weird that a "more complicated" result about polynomials ends up in a "more simple" namespace about monoids with zero.)

[tb65536]

Splits.splits_of_dvd sounds reasonable to me.

[YaelDillies]

I disagree here. Using Foo.of_bar to mean Foo _ -> Bar _ -> Foo _ is a common and understood pattern. As such, this rename is both out of scope for this PR and (IMO) a regression.

[jcommelin]

Thanks 🎉

bors merge

[mathlib-bors]

Pull request successfully merged into master.

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