Fix Google-internal common.collect tests under an Android emulator.

The primary change comes as a followup to cl/543468006: Now that the Google-internal `ImmutableTable` declares [methods with Java 8+ types in their signatures](#6567), we get a `NoClassDefFoundError` when performing reflection on the class under old Android emulators. We perform reflection only when (a) using `NullPointerTester` or (b) using serialization. So we (a) stop running `NullPointerTester` under an Android emulator (though we continue to run the same `guava-android` test under a JVM) and (b) specify a `serialVersionUID` so that serialization doesn't need to compute one. (Specifying `serialVersionUID` was our MO for a while. Perhaps we just got careless, and perhaps we should be more diligent. Alternatively, perhaps we should change the `serialVersionUID` every release or so so as to encourage people [not to persist serialized data](https://github.com/google/guava#important-warnings). I at least went to a tiny bit of effort to keep `guava-jre` and `guava-android` on different `serialVersionUID` values, though maybe that's more likely to cause needless trouble someday than to prevent it?)

The other change is to avoid running another GC test under an Android emulator. We'd originally done this for one copy of `AbstractIteratorTester` in cl/444929745, but for whatever reason, we didn't need it for the other copy until (I assume) cl/546307327 and its switch to a different emulator version.

RELNOTES=n/a
PiperOrigin-RevId: 550670580

android/guava-tests/test/com/google/common/collect/AbstractIteratorTest.java

@@ -137,6 +137,7 @@ public Integer computeNext() {
 
 
   @GwtIncompatible // weak references
+  @AndroidIncompatible // depends on details of GC
   public void testFreesNextReference() {
     Iterator<Object> itr =
         new AbstractIterator<Object>() {

android/guava-tests/test/com/google/common/collect/ImmutableTableTest.java

@@ -479,4 +479,33 @@ public void testOverflowCondition() {
     }
     assertTrue(builder.build() instanceof SparseImmutableTable);
   }
+
+  @GwtIncompatible // NullPointerTester
+  @Override
+  public void testNullPointerInstance() {
+    if (isAndroid()) {
+      /*
+       * NPT fails under the old versions of Android we test under because it performs reflection on
+       * ImmutableTable, which declares static methods that refer to Collector, which is unavailable
+       * under such versions.
+       *
+       * We use a runtime check here instead of @AndroidIncompatible: @AndroidIncompatible operates
+       * by stripping annotated methods entirely, and if we strip this method, then JUnit would just
+       * run the supermethod as usual.
+       *
+       * TODO: b/292578973: Use @AndroidIncompatible if we change our system to keep the methods in
+       * place but to have the test runner skip them. However, note that if we choose to *both*
+       * strip the methods *and* have the test runner not run them (for some unusual cases in which
+       * we don't run the stripping test for technical reasons), then we'd be back to the problem
+       * described above, since the supermethod is *not* annotated @AndroidIncompatible (since it
+       * works fine with the other Table implementations).
+       */
+      return;
+    }
+    super.testNullPointerInstance();
+  }
+
+  private static boolean isAndroid() {
+    return System.getProperty("java.runtime.name", "").contains("Android");
+  }
 }

android/guava/src/com/google/common/collect/ImmutableTable.java

@@ -463,4 +463,6 @@ final Object writeReplace() {
   private void readObject(ObjectInputStream stream) throws InvalidObjectException {
     throw new InvalidObjectException("Use SerializedForm");
   }
+
+  private static final long serialVersionUID = 0xdecaf;
 }

guava-tests/test/com/google/common/collect/AbstractIteratorTest.java

@@ -137,6 +137,7 @@ public Integer computeNext() {
 
 
   @GwtIncompatible // weak references
+  @AndroidIncompatible // depends on details of GC
   public void testFreesNextReference() {
     Iterator<Object> itr =
         new AbstractIterator<Object>() {

guava-tests/test/com/google/common/collect/ImmutableTableTest.java

@@ -485,4 +485,33 @@ public void testOverflowCondition() {
     }
     assertTrue(builder.build() instanceof SparseImmutableTable);
   }
+
+  @GwtIncompatible // NullPointerTester
+  @Override
+  public void testNullPointerInstance() {
+    if (isAndroid()) {
+      /*
+       * NPT fails under the old versions of Android we test under because it performs reflection on
+       * ImmutableTable, which declares static methods that refer to Collector, which is unavailable
+       * under such versions.
+       *
+       * We use a runtime check here instead of @AndroidIncompatible: @AndroidIncompatible operates
+       * by stripping annotated methods entirely, and if we strip this method, then JUnit would just
+       * run the supermethod as usual.
+       *
+       * TODO: b/292578973: Use @AndroidIncompatible if we change our system to keep the methods in
+       * place but to have the test runner skip them. However, note that if we choose to *both*
+       * strip the methods *and* have the test runner not run them (for some unusual cases in which
+       * we don't run the stripping test for technical reasons), then we'd be back to the problem
+       * described above, since the supermethod is *not* annotated @AndroidIncompatible (since it
+       * works fine with the other Table implementations).
+       */
+      return;
+    }
+    super.testNullPointerInstance();
+  }
+
+  private static boolean isAndroid() {
+    return System.getProperty("java.runtime.name", "").contains("Android");
+  }
 }

guava/src/com/google/common/collect/ImmutableTable.java

@@ -512,4 +512,6 @@ final Object writeReplace() {
   private void readObject(ObjectInputStream stream) throws InvalidObjectException {
     throw new InvalidObjectException("Use SerializedForm");
   }
+
+  private static final long serialVersionUID = 0xcafebabe;
 }