feat(AlgebraicGeometry): Define algebraic cycles

[Raph-DG]

In this PR we define the notion of algebraic cycles on a scheme, and define the pushforward of an algebraic cycle by a quasicompact morhphism. This was originally defined in #26304, but after some refactoring it was decided that it would be best to split this definition into a separate PR.

• depends on: feat(AlgebraicGeometry): Pushforward of algebraic cycles #26304

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[github-actions]

PR summary cc26c21489

Import changes for modified files

No significant changes to the import graph

Import changes for all files

Files	Import difference
Mathlib.Topology.LocallyFinsupp.Pushforward (new file)	933
Mathlib.AlgebraicGeometry.AlgebraicCycle (new file)	2316

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Declarations diff

+ AlgebraicCycle
+ PreimageSupportFinite
+ _root_.AlgebraicGeometry.Scheme.Hom.degree
+ _root_.AlgebraicGeometry.Scheme.Hom.preimageSupportFinite
+ _root_.IsProperMap.preimageSupportFinite
+ inter_preimageSupport_nonempty_finite
+ map
+ mapAux
+ map_homogeneous
+ map_id
+ map_locally_finite
+ moduleResidueFieldExtension
+ preimageSupport
+ preimageSupportFinite_id
+ pushforward

You can run this locally as follows

## summary with just the declaration names:
./scripts/pr_summary/declarations_diff.sh <optional_commit>

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

The doc-module for scripts/pr_summary/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/reporting/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).

[mathlib-dependent-issues]

This PR/issue depends on:

• feat(AlgebraicGeometry): Pushforward of algebraic cycles #26304
  By Dependent Issues (🤖). Happy coding!