Expose AbstractDependencyFilter from internal to public

[Goooler]

Refs

• shadowJar breaks Gradle artifact transforms #882
• Fix interaction with Gradle artifact transforms #1345.

---

• CHANGELOG's "Unreleased" section has been updated, if applicable.

[Copilot]

Pull Request Overview

This PR exposes the AbstractDependencyFilter class from the internal package to the public API, making it available as a nested class within DependencyFilter. The change enables external users to extend the abstract dependency filter functionality.

• Moves AbstractDependencyFilter from internal package to public API as a nested class
• Updates existing internal implementations to use the new public location
• Documents the change in the changelog with the new public access path

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/main/kotlin/com/github/jengelman/gradle/plugins/shadow/tasks/DependencyFilter.kt	Adds AbstractDependencyFilter as a public nested class with additional imports
src/main/kotlin/com/github/jengelman/gradle/plugins/shadow/internal/MinimizeDependencyFilter.kt	Updates inheritance to use the new public DependencyFilter.AbstractDependencyFilter
src/main/kotlin/com/github/jengelman/gradle/plugins/shadow/internal/DefaultDependencyFilter.kt	Updates inheritance to use the new public DependencyFilter.AbstractDependencyFilter
src/main/kotlin/com/github/jengelman/gradle/plugins/shadow/internal/AbstractDependencyFilter.kt	Removes the entire internal implementation (file deleted)
docs/changes/README.md	Documents the API change in the unreleased section
api/shadow.api	Updates the public API signature file to include the new public class