Optimize CI by using a custom Docker container with pre-installed dependencies.

This change introduces a Docker container (`.ci/container/Dockerfile`) that pre-installs:
- OpenJDK 8 (ZuluFX), 11, 17, 21, and 25 (Zulu).
- Android SDK (command-line tools, platform-tools, build-tools) and NDK dependencies.
- Ant, Maven, Python 3.
- Codename One binaries (`cn1-binaries`).
- Required libraries for headless UI testing (xvfb, libgl1-mesa-dri, libncurses6).

Updates `pr.yml`, `ant.yml`, and `scripts-android.yml` to run jobs inside this container (`ghcr.io/codenameone/codenameone/ci-container:latest`), removing redundant setup steps (JDK download, tool installation) to improve build speed and reproducibility.

The workflow `.github/workflows/build-container.yml` is added to build and push this container image to GHCR, ensuring the image tag is always lowercase to comply with registry requirements.

Also updates `scripts/setup-workspace.sh` to respect the `CN1_BINARIES` environment variable and handle the pre-configured environment correctly.

Author: google-labs-jules[bot]

.ci/container/Dockerfile

@@ -73,8 +73,11 @@ ENV PATH=${ANDROID_HOME}/cmdline-tools/latest/bin:${ANDROID_HOME}/platform-tools
 
 # Accept licenses and install packages
 # Note: sdkmanager requires Java 11+ to run. We use JAVA17_HOME for this step.
-RUN yes | JAVA_HOME=${JAVA17_HOME} sdkmanager --licenses && \
-    JAVA_HOME=${JAVA17_HOME} sdkmanager "platform-tools" "platforms;android-31" "build-tools;31.0.0"
+# We dynamically locate Zulu 17 to ensure the correct path is used.
+RUN export JAVA17_REAL=$(find /usr/lib/jvm -maxdepth 1 -name "zulu*17*" -type d | head -n 1) && \
+    echo "Using JDK 17 at: $JAVA17_REAL" && \
+    yes | JAVA_HOME=$JAVA17_REAL sdkmanager --licenses && \
+    JAVA_HOME=$JAVA17_REAL sdkmanager "platform-tools" "platforms;android-31" "build-tools;31.0.0"
 
 # Set Default JAVA_HOME to Java 8 (as per user requirement for builds)
 ENV JAVA_HOME=/usr/lib/jvm/zulu8-fx