fix #20232

Context

Update AbstractMavenPublisher to check if each artifact requires checksum files.

Create MavenArtifactInternal as a common parent for AbstractMavenArtifact and SerializableMavenArtifact. It has a method, enableChecksumFileGeneration(). When derived artifacts (signatures) are added to a Maven publication (by the signing plugin), Gradle will disable checksum file generation for them.

Creating MavenArtifactInternal was necessary, otherwise it would have to be added to the existing common parent of AbstractMavenArtifact and SerializableMavenArtifact, PublicationInternal, which is also a parent for Ivy types. To keep the change small, this branch only modifies Maven publications.

Contributor Checklist

• Review Contribution Guidelines.
• Make sure that all commits are signed off to indicate that you agree to the terms of Developer Certificate of Origin.
• Make sure all contributed code can be distributed under the terms of the Apache License 2.0, e.g. the code was written by yourself or the original code is licensed under a license compatible to Apache License 2.0.
• Check "Allow edit from maintainers" option in pull request so that additional changes can be pushed by Gradle team.
• Provide integration tests (under <subproject>/src/integTest) to verify changes from a user perspective.
• Provide unit tests (under <subproject>/src/test) to verify logic.
• Update User Guide, DSL Reference, and Javadoc for public-facing changes.
• Ensure that tests pass sanity check: ./gradlew sanityCheck.
• Ensure that tests pass locally: ./gradlew <changed-subproject>:quickTest.

Reviewing cheatsheet

Before merging the PR, comments starting with

• ❌ ❓must be fixed
• 🤔 💅 should be fixed
• 💭 may be fixed
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