Update GitHub workflows to use JDK 21 (Oracle)

All workflows now use JDK 21 with the Oracle distribution instead of JDK 17 or 11 with Temurin. This ensures consistency and leverages the latest Java features and security updates.

.github/workflows/gh-mvn-publish.yml

@@ -14,11 +14,11 @@ jobs:
 
     steps:
       - uses: actions/checkout@v5
-      - name: Set up JDK 17
+      - name: Set up JDK 21
         uses: actions/setup-java@v5
         with:
-          java-version: '17'
-          distribution: 'temurin'
+          java-version: '21'
+          distribution: 'oracle'
           server-id: github
           settings-path: ${{ github.workspace }}