chore (Algebra.PUnitInstances): split file into `Algebra`, `Order`, and `Module` instance files

[mattrobball]

When we need algebra structures on PUnit, we should be more surgical about what we are importing.

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[github-actions[bot]]

PR summary e200a23ca2

Import changes for modified files

Dependency changes

File	Base Count	Head Count	Change
Mathlib.Algebra.Category.MonCat.Basic	466	426	-40 (-8.58%)
Mathlib.CategoryTheory.Monoidal.Mon_	495	460	-35 (-7.07%)
Mathlib.Algebra.Category.Grp.Basic	468	442	-26 (-5.56%)
Mathlib.GroupTheory.Coprod.Basic	557	542	-15 (-2.69%)
Mathlib.Algebra.Ring.BooleanRing	509	499	-10 (-1.96%)

Import changes for all files

Files	Import difference
Too many changes (2023)!

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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/no_lost_declarations.sh short <optional_commit>

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

[github-actions[bot]]

🚀 Pull request has been placed on the maintainer queue by grunweg.

[github-actions[bot]]

🚀 Pull request has been placed on the maintainer queue by grunweg.

[jcommelin]

bors d+

[mathlib-bors[bot]]

:v: mattrobball can now approve this pull request. To approve and merge a pull request, simply reply with bors r+. More detailed instructions are available here.

[mattrobball]

bors merge

[mathlib-bors[bot]]

Pull request successfully merged into master.

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