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

@@ -49,14 +49,14 @@ RUN git clone --depth=1 https://github.com/codenameone/cn1-binaries /opt/cn1-bin
 # Set Environment Variables for JDKs (Paths for apt installed JDKs usually symlinked to /usr/lib/jvm/zulu-XX-amd64)
 ENV JAVA8_HOME=/usr/lib/jvm/zulu8-fx
 ENV JDK8_HOME=/usr/lib/jvm/zulu8-fx
-ENV JAVA11_HOME=/usr/lib/jvm/zulu-11-amd64
-ENV JDK11_HOME=/usr/lib/jvm/zulu-11-amd64
-ENV JAVA17_HOME=/usr/lib/jvm/zulu-17-amd64
-ENV JDK17_HOME=/usr/lib/jvm/zulu-17-amd64
-ENV JAVA21_HOME=/usr/lib/jvm/zulu-21-amd64
-ENV JDK21_HOME=/usr/lib/jvm/zulu-21-amd64
-ENV JAVA25_HOME=/usr/lib/jvm/zulu-25-amd64
-ENV JDK25_HOME=/usr/lib/jvm/zulu-25-amd64
+ENV JAVA11_HOME=/usr/lib/jvm/zulu11-ca-amd64
+ENV JDK11_HOME=/usr/lib/jvm/zulu11-ca-amd64
+ENV JAVA17_HOME=/usr/lib/jvm/zulu17-ca-amd64
+ENV JDK17_HOME=/usr/lib/jvm/zulu17-ca-amd64
+ENV JAVA21_HOME=/usr/lib/jvm/zulu21-ca-amd64
+ENV JDK21_HOME=/usr/lib/jvm/zulu21-ca-amd64
+ENV JAVA25_HOME=/usr/lib/jvm/zulu25-ca-amd64
+ENV JDK25_HOME=/usr/lib/jvm/zulu25-ca-amd64
 
 # Install Android SDK
 ENV ANDROID_HOME=/opt/android-sdk