Add process termination support for Android plugin

Introduces a 'terminate' method to the Android plugin and Dart interface, allowing the app to kill its process for a clean restart. Also disables GIL management in _withGIL due to potential issues with embedded CPython state after Dart isolate restarts.

Author: FeodorFitsner

src/serious_python_android/android/src/main/java/com/flet/serious_python_android/AndroidPlugin.java

@@ -5,6 +5,9 @@
 import androidx.annotation.NonNull;
 import android.system.Os;
 import android.content.Intent;
+import android.os.Handler;
+import android.os.Looper;
+import android.os.Process;
 
 import io.flutter.embedding.engine.plugins.FlutterPlugin;
 import io.flutter.embedding.engine.plugins.activity.ActivityAware;
@@ -80,6 +83,13 @@ public void onMethodCall(@NonNull MethodCall call, @NonNull Result result) {
       } catch (Exception e) {
         result.error("Error", e.getMessage(), null);
       }
+    } else if (call.method.equals("terminate")) {
+      // Terminate the process shortly after responding to Dart.
+      result.success(null);
+      new Handler(Looper.getMainLooper()).postDelayed(
+          () -> Process.killProcess(Process.myPid()),
+          100
+      );
     } else {
       result.notImplemented();
     }

src/serious_python_android/lib/serious_python_android.dart

@@ -95,4 +95,12 @@ class SeriousPythonAndroid extends SeriousPythonPlatform {
     return runPythonProgramFFI(
         sync ?? false, "libpython3.12.so", appPath, script ?? "");
   }
+
+  @override
+  void terminate() {
+    // CPython is embedded in-process; after Flutter engine/Dart isolate restarts,
+    // native CPython state (including the GIL) can be left in a bad state.
+    // Killing the process is the most reliable way to guarantee a clean start.
+    methodChannel.invokeMethod<String>('terminate');
+  }
 }

src/serious_python_android/lib/src/cpython.dart

@@ -53,12 +53,13 @@ void _debug(String message) {
 }
 
 T _withGIL<T>(CPython cpython, T Function() action) {
-  final gil = cpython.PyGILState_Ensure();
-  try {
-    return action();
-  } finally {
-    cpython.PyGILState_Release(gil);
-  }
+//   final gil = cpython.PyGILState_Ensure();
+//   try {
+//     return action();
+//   } finally {
+//     cpython.PyGILState_Release(gil);
+//   }
+  return action();
 }
 
 Future<String> runPythonProgramFFI(bool sync, String dynamicLibPath,