[Merged by Bors] - chore: move files into Analysis.Normed.Algebra

[j-loreaux]

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This is meant to be one part of a larger organizational project for Analysis.NormedSpace. This moves files related to algebras into their own folder.

[github-actions]

PR summary 2f79a6d164

Import changes for modified files

No significant changes to the import graph

Import changes for all files

Files	Import difference
Mathlib.Analysis.NormedSpace.Algebra	-1907
Mathlib.Analysis.NormedSpace.Spectrum	-1905
Mathlib.Analysis.NormedSpace.TrivSqZeroExt	-1441
Mathlib.Analysis.NormedSpace.UnitizationL1	-1378
Mathlib.Analysis.NormedSpace.Unitization	-1272
Mathlib.Analysis.Normed.Algebra.Unitization	1272
Mathlib.Analysis.Normed.Algebra.UnitizationL1	1378
Mathlib.Analysis.Normed.Algebra.TrivSqZeroExt	1441
Mathlib.Analysis.Normed.Algebra.Spectrum	1905
Mathlib.Analysis.Normed.Algebra.Basic	1907

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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/declarations_diff.sh <optional_commit>

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

[grunweg]

Grouping these files looks reasonable. The new folder "Algebra" is ambiguous (and could refer to the mathematical object as well to the area); I don't see an obvious alternative, though. Let's have some more eyes on this:
maintainer merge

[github-actions]

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

[riccardobrasca]

Thanks!

bors merge

[mathlib-bors]

Pull request successfully merged into master.

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