feat(Geometry/Euclidean/Projection): projection onto sup

[jsm28]

Add a lemma that, if the orthogonal projections of a point onto two subspaces are equal, so is the projection onto their supremum.

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• depends on: feat(Geometry/Euclidean/Projection): characteristic property #30698
• depends on: [Merged by Bors] - feat(LinearAlgebra/AffineSpace/AffineSubspace/Defs): nonempty sup #30699

[github-actions]

PR summary 560872a203

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

+ coe_orthogonalProjection_eq_iff_mem
+ orthogonalProjection_eq_iff_mem
+ orthogonalProjection_eq_orthogonalProjection_iff_vsub_mem
+ orthogonalProjection_sup_of_orthogonalProjection_eq

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:

• feat(Geometry/Euclidean/Projection): characteristic property #30698
• [Merged by Bors] - feat(LinearAlgebra/AffineSpace/AffineSubspace/Defs): nonempty sup #30699
  By Dependent Issues (🤖). Happy coding!