Support linux aarch64 for Dart and Flutter (#2342)

Adds support for building and packaging Linux AArch64 (arm64) artifacts alongside x64 for Dart/Flutter plugins.

- Detects host architecture in CMake and adjusts library paths
- Extends test workflows to run on an ARM runner and handle linux-aarch64 paths
- Splits release pipeline into separate x64 and aarch64 build/package jobs

dart-api-examples/vad/bin/init.dart

@@ -25,6 +25,14 @@ Future<void> initSherpaOnnx() async {
     exit(1);
   }
 
-  final libPath = p.join(p.dirname(p.fromUri(uri)), '..', platform);
+  var libPath = p.join(p.dirname(p.fromUri(uri)), '..', platform);
+  if (platform == 'linux') {
+    final arch = Platform.version.contains('arm64') ||
+            Platform.version.contains('aarch64')
+        ? 'aarch64'
+        : 'x64';
+    libPath = p.join(p.dirname(p.fromUri(uri)), '..', platform, arch);
+  }
+
   sherpa_onnx.initBindings(libPath);
 }