feat: define Matrix.ProjGenLinGroup

[urkud]

---

• depends on: feat(GeneralLinearGroup): define GeneralLinearGroup.scalar #34986

[mathlib-dependent-issues]

This PR/issue depends on:

• feat(GeneralLinearGroup): define GeneralLinearGroup.scalar #34986
  By Dependent Issues (🤖). Happy coding!

[github-actions]

PR summary de6d0d0211

Import changes for modified files

No significant changes to the import graph

Import changes for all files

Files	Import difference
Mathlib.LinearAlgebra.Matrix.GeneralLinearGroup.Projective (new file)	1526

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Declarations diff

+ ProjGenLinGroup
+ center_eq_range_scalar
+ det_scalar
+ induction_on
+ ker_mk
+ lift
+ lift_comp_mk
+ lift_mk
+ mem_center_iff_val_mem_range_scalar
+ mk
+ mk_scalar
+ mk_smul
+ mk_surjective
+ mulActionOfGL
+ scalar
+ signDet
+ signDet_mk
+ val_signDet_mk

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).