convert RuntimeInstrumentationTest to kotlin (#15079)

### Summary
All tests are written in kotlin except
extension/android/executorch_android/src/androidTest/java/org/pytorch/executorch/RuntimeInstrumentationTest.java,
this change converts this test from java to kotlin so that all tests are
now kotlin.

### Test plan
Run test locally.

Co-authored-by: Haiting Pu <[email protected]>

Author: phaiting

extension/android/executorch_android/src/androidTest/java/org/pytorch/executorch/RuntimeInstrumentationTest.java

@@ -0,0 +1,34 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+package org.pytorch.executorch
+
+import androidx.test.ext.junit.runners.AndroidJUnit4
+import org.junit.Assert
+import org.junit.Test
+import org.junit.runner.RunWith
+
+/** Unit tests for [ExecuTorchRuntime].  */
+@RunWith(AndroidJUnit4::class)
+class RuntimeInstrumentationTest {
+    @Test
+    fun testRuntimeApi() {
+        val ops = ExecuTorchRuntime.getRegisteredOps()
+        val backends = ExecuTorchRuntime.getRegisteredBackends()
+
+        Assert.assertNotNull(ops)
+        Assert.assertNotNull(backends)
+
+        for (op in ops) {
+            Assert.assertNotNull(op)
+        }
+
+        for (backend in backends) {
+            Assert.assertNotNull(backend)
+        }
+    }
+}