Implement java.io.File in JavaAPI with native support for ParparVM

- Added full implementation of `java.io.File` in `vm/JavaAPI` delegating to native methods.
- Added native implementation in `vm/ByteCodeTranslator/src/java_io_File.m` supporting both iOS (`NSFileManager`) and Linux/POSIX.
- Updated `ByteCodeTranslator` to package the new native source file.
- Patched `vm/ByteCodeTranslator/src/nativeMethods.m` and `cn1_globals.m` to support compilation on Linux (added guards and stubs).
- Added `vm/tests/src/test/java/com/codename1/tools/translator/FileClassIntegrationTest.java` to verify the implementation.
- Fixed string concatenation issues in `vm/JavaAPI` exception constructors to resolve C compilation errors.
- Added `vm/JavaAPI/src/java/util/Objects.java` to resolve missing dependency during integration tests.
- Removed conflicting `java.util.Objects` stub generation from `LambdaIntegrationTest`.

Author: google-labs-jules[bot]

vm/tests/src/test/java/com/codename1/tools/translator/LambdaIntegrationTest.java

@@ -154,7 +154,6 @@ private void compileJavaAPI(Path outputDir) throws Exception {
         // Add stubs for java.lang.invoke
         Path stubsDir = Files.createTempDirectory("java-lang-invoke-stubs");
         sources.addAll(generateJavaLangInvokeStubs(stubsDir));
-        sources.addAll(generateJavaUtilStubs(stubsDir));
 
         JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
         List<String> args = new ArrayList<>();
@@ -177,22 +176,6 @@ private void compileJavaAPI(Path outputDir) throws Exception {
         assertEquals(0, result, "JavaAPI should compile");
     }
 
-    private List<String> generateJavaUtilStubs(Path stubsDir) throws IOException {
-        List<String> stubFiles = new ArrayList<>();
-        Path utilPkg = stubsDir.resolve("java/util");
-        Files.createDirectories(utilPkg);
-
-        // Objects
-        Path objs = utilPkg.resolve("Objects.java");
-        Files.write(objs, ("package java.util;\n" +
-                "public class Objects {\n" +
-                "    public static <T> T requireNonNull(T obj) { if (obj == null) throw new NullPointerException(); return obj; }\n" +
-                "}").getBytes(StandardCharsets.UTF_8));
-        stubFiles.add(objs.toString());
-
-        return stubFiles;
-    }
-
     private List<String> generateJavaLangInvokeStubs(Path stubsDir) throws IOException {
         List<String> stubFiles = new ArrayList<>();
         Path invokePkg = stubsDir.resolve("java/lang/invoke");