chore: Maintenance for 3.1.1 (Fix CME, update wrapper, secure test deps, clean build script)

[haeusler]

This PR introduces a few safe maintenance updates and bug fixes to prepare for a 3.1.1 patch release.

Changes Included:

• Fix ConcurrentModificationException: Eagerly evaluates configurations to a static list (.toList()) in CheckSnapshotDependencies.groovy. This prevents crashes when using the plugin alongside frameworks (like Quarkus 3.25.1+) that dynamically mutate configurations during evaluation. (Fixes ConcurrentModificationException in checkSnapshotDependencies when used with Quarkus 3.25.1+ (Gradle component variants) #406)
• Build Script Modernization:
  • Removed legacy buildscript block and resolved plugin version conflicts.
  • Replaced deprecated testCompile with testImplementation.
  • Explicitly set sourceCompatibility and targetCompatibility to 1.8 to safeguard Java 8 baseline compatibility.
• Update Test Dependencies: Bumped guava to 32.0.1-jre to resolve known CVEs in the test harness.
• Matrix & Runner Changes:
  • Expanded testing matrix to cover Gradle 6-9 across Java 8, 11, 17, and 21.
  • Configured CI to build always build the plugin with Java 8, while testing against the full matrix of Java versions via Gradle Toolchains.
  • Fixed artifact naming conflicts in the matrix to ensure consolidated JUnit reporting.

Checklist

• Test suite passes locally

[Copilot]

Pull request overview

Maintenance updates to prepare the Gradle Release plugin for a 3.1.1 patch release, including a fix for checkSnapshotDependencies failing with ConcurrentModificationException in builds where configurations mutate during evaluation (e.g., Quarkus component variants).

Changes:

• Prevent ConcurrentModificationException by iterating over snapshot lists of configurations in CheckSnapshotDependencies.
• Modernize the plugin’s own build (plugins DSL cleanup, dependency config updates, updated test deps).
• Update the Gradle wrapper and CI workflow actions.

Reviewed changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/main/groovy/net/researchgate/release/tasks/CheckSnapshotDependencies.groovy	Snapshot configuration collections via toList() to avoid concurrent modification during iteration.
build.gradle	Removes legacy buildscript usage, updates plugin/dependency declarations, and bumps wrapper version.
gradle/wrapper/gradle-wrapper.properties	Updates wrapper distribution URL to Gradle 6.9.4 (but drops SHA256 verification).
gradlew	Updates the generated POSIX wrapper script content.
.github/workflows/tests.yaml	Updates GitHub Actions versions and switches JDK distribution to Temurin.

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[Copilot]

Pull request overview

Copilot reviewed 4 out of 5 changed files in this pull request and generated 2 comments.

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