move junit tests to android_test (#6761)

Move JUnit tests to android_test to centralize both unit tests and instrumentation tests.

Author: davidlin54

extension/android/build.gradle

@@ -20,6 +20,5 @@ task makeJar(type: Jar) {
     dependencies {
         implementation 'com.facebook.fbjni:fbjni-java-only:0.2.2'
         implementation 'com.facebook.soloader:nativeloader:0.10.5'
-        testImplementation 'junit:junit:4.13.2'
     }
 }

extension/android/src/test/java/org/pytorch/executorch/EValueTest.java renamed to extension/android_test/src/test/java/org/pytorch/executorch/EValueTest.java

@@ -129,7 +129,7 @@ public void testOptionalTensorListValue() {
         Optional.of(Tensor.fromBlob(data[1], shape[1])));
     assertTrue(evalue.isOptionalTensorList());
 
-    assertTrue(evalue.toOptionalTensorList()[0].isEmpty());
+    assertTrue(!evalue.toOptionalTensorList()[0].isPresent());
 
     assertTrue(evalue.toOptionalTensorList()[1].isPresent());
     assertTrue(Arrays.equals(evalue.toOptionalTensorList()[1].get().shape, shape[0]));