Flat records for limits/colimits

[TOTBWF]

Description

This PR flattens out Binary-products et. al into flat records to get better printing.

Currently, this is a draft to get API feedback!

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[Lavenza]

Pull request preview

[ncfavier]

Could we have a test/reproducer for the printing issues with, say, binary products?

[TOTBWF]

I think @plt-amy had a good real world example in https://gist.github.com/plt-amy/9f1efaaef2fe15baf4965be21e60994b, we could use the code that generated the nightmare for that

[ncfavier]

I guess things like δ-natural can serve as test cases. Without this PR the goal is

is-product.⟨ Product.has-is-product (all-products y y) , id ⟩
      id
      ∘ f
      ≡
      is-product.⟨ Product.has-is-product (all-products y y) ,
      f ∘ Product.π₁ (all-products x x) ⟩
      (f ∘ Product.π₂ (all-products x x))
      ∘ is-product.⟨ Product.has-is-product (all-products x x) , id ⟩ id

With this PR it becomes ⟨ id , id ⟩ ∘ f ≡ ⟨ f ∘ π₁ , f ∘ π₂ ⟩ ∘ ⟨ id , id ⟩. Much better!