Update Docker base image versions

Author: anuruddhal

compiler-plugin/src/main/java/io/ballerina/c2c/DockerGenConstants.java

@@ -26,12 +26,11 @@ public class DockerGenConstants {
     public static final String EXECUTABLE_JAR = ".jar";
     public static final String REGISTRY_SEPARATOR = "/";
     public static final String TAG_SEPARATOR = ":";
-    public static final String JRE_SLIM_BASE = "ballerina/jvm-runtime:2.0";
-    public static final String NATIVE_BUILDER_IMAGE = "ghcr.io/graalvm/native-image-community:17-ol8";
+    public static final String JRE_SLIM_BASE = "ballerina/jvm-runtime:3.0";
+    public static final String NATIVE_BUILDER_IMAGE = "ghcr.io/graalvm/native-image-community:21-ol8";
     public static final String NATIVE_RUNTIME_BASE_IMAGE = "gcr.io/distroless/base";
     public static final int MAX_BALLERINA_LAYERS = 110;
 
     public static final String SCHEMA_FILE_NAME = "c2c-schema.json";
-    public static final String WINDOWS_SEPARATOR = "\\";
     public static final String REFLECT_JSON_FILE = "reflect-config.json";
 }