[Merged by Bors] - feat: 'and' and 'exist' commute for Antitone or Monotone properties

[scholzhannah]

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The lemma Filter.exists_mem_and_iff is very similar to this.
But I have unfortunately not managed to come up with a sensible generalisation that covers that lemma as well.
Please do suggest generalisations!

[github-actions]

PR summary 5af36d12e8

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

+ exists_and_iff_of_antitone
+ exists_and_iff_of_monotone

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.

[Ruben-VandeVelde]

maintainer merge

[github-actions]

🚀 Pull request has been placed on the maintainer queue by Ruben-VandeVelde.

[fpvandoorn]

bors merge

[mathlib-bors]

Pull request successfully merged into master.

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