fix: support import module in removeUnusedImports (GJF 1.30.0)

[arimu1]

Problem

java { removeUnusedImports() } / <removeUnusedImports/> fails on sources that use Java's import module (JEP 511), e.g.:

import module java.base;

class ModuleImportTest {
  void test() {
    UUID.randomUUID();
  }
}

with:

LINE_UNDEFINED removeUnusedImports(java.lang.IllegalArgumentException)
object of type com.sun.tools.javac.tree.JCTree$JCModuleImport is not an instance of com.sun.tools.javac.tree.JCTree$JCImport

Root cause: default google-java-format was still 1.28.0. Module-import support landed in google-java-format 1.30.0 (google/google-java-format#1213 / #1297), which skips JCModuleImport in RemoveUnusedImports instead of casting every import tree to JCImport.

Fixes #2890

Solution

• Bump default google-java-format 1.28.0 → 1.30.0 (first release with import module support)
• Require at least 1.30.0 when Spotless runs on JVM 25+ (Jvm.Support.addMin)
• Align gradle/libs.versions.toml compile coordinate with the new default
• Regression tests for module imports (JDK 25+) and the new JVM 25 minimum

Users who pin an older GJF version on JVM 25 get a clear lint instead of a ClassCastException mid-format.

Testing

# JDK 21 (module-import parse tests skipped — javac < 25 cannot parse import module)
./gradlew :testlib:test \
  --tests 'com.diffplug.spotless.java.RemoveUnusedImportsStep_withGoogleJavaFormatTest' \
  --tests 'com.diffplug.spotless.java.GoogleJavaFormatStepTest'
# 16 tests, 4 skipped — all green

# JDK 25
JAVA_HOME=…/jdk-25 ./gradlew :testlib:test \
  --tests 'com.diffplug.spotless.java.RemoveUnusedImportsStep_withGoogleJavaFormatTest' \
  --tests 'com.diffplug.spotless.java.GoogleJavaFormatStepTest'
# moduleImports + versionBelowMinOnJava25IsNotAllowed green

Platform: macOS aarch64, Temurin 21.0.12 + Temurin 25.0.4

Checklist

• summary under [Unreleased] in CHANGES.md, plugin-gradle/CHANGES.md, and plugin-maven/CHANGES.md
• link to issue java.removeUnusedImports does not handle import module correctly #2890
• allow edits from maintainers