chore(Tactic/Linters): remove public section

[grunweg]

Mostly as a learning exercise for me to understand the module system better.

---

• depends on: [Merged by Bors] - chore: turn on module system in MathlibTest #31823 (to make visibility changes just for tests a conscious choice)

[github-actions]

PR summary 082440f5b2

Import changes for modified files

No significant changes to the import graph

Import changes for all files

Files	Import difference

---

Declarations diff

- ErrorFormat
- Lean.Name.isLocal
- copyrightHeaderChecks
- deprecatedNoSince
- directoryDependencyCheck
- extractOpenNames
- findImports
- getDeclModifiers
- getImportIds
- isCDot?
- isSetOption
- mkWindow
- structureInType

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.

---

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).

[grunweg]

One might argue that this is useful public API (as evidenced by the unit tests). If so, I'll be happy to remove the comment.

[grunweg]

As above

[grunweg]

!bench

[grunweg]

(Just in case, I would be a bit surprised to see any effect.)

[leanprover-radar]

Benchmark results for 97e228b against 6a54a80 are in! @grunweg

[leanprover-bot]

Here are the benchmark results for commit 97e228b.
There were no significant changes against commit 6a54a80.

[github-actions]

File	Instructions	%
build	+287.39⬝10⁹	(+0.16%)
lint	-1.43⬝10⁹	(-0.01%)

2 files, Instructions +1.0⬝10⁹

File	Instructions	%
Mathlib.CategoryTheory.Preadditive.Biproducts	+1.183⬝10⁹	(+1.75%)
Mathlib.Tactic.CC.Lemmas	+1.117⬝10⁹	(+33.70%)

CI run Lakeprof report

[mathlib4-dependent-issues-bot]

This PR/issue depends on:

• [Merged by Bors] - chore: turn on module system in MathlibTest #31823
  By Dependent Issues (🤖). Happy coding!