Make most transformers pattern-filterable

[Goooler]

Refs #1849.

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

[Copilot]

Pull request overview

This PR makes several built-in resource transformers extend PatternFilterableResourceTransformer, allowing their patternSet to be publicly configured while preserving their default matching behavior.

Changes:

• Converts manifest, Log4j2 plugin cache, Groovy extension module, and Plexus components transformers to pattern-filterable implementations.
• Adds public constructors accepting PatternSet where applicable and updates the API snapshot.
• Documents the newly exposed patternSet APIs in the Unreleased changelog.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/main/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/ManifestResourceTransformer.kt	Makes manifest transformation pattern-filterable with case-insensitive default manifest matching.
src/main/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/ManifestAppenderTransformer.kt	Makes manifest appending pattern-filterable with case-insensitive default manifest matching.
src/main/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/Log4j2PluginsCacheFileTransformer.kt	Makes Log4j2 plugin cache transformation pattern-filterable.
src/main/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/GroovyExtensionModuleTransformer.kt	Makes Groovy extension module transformation pattern-filterable.
src/main/kotlin/com/github/jengelman/gradle/plugins/shadow/transformers/ComponentsXmlResourceTransformer.kt	Makes Plexus components XML transformation pattern-filterable.
docs/changes/README.md	Adds Unreleased changelog entries for the newly exposed pattern sets.
api/shadow.api	Updates the public API baseline for the new inheritance and constructors.

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