AAPT2: Support CtsContentTestCases build

- Add <feature-group> to ManifestFixer.
- Support <meta-data> in <instrumentation>
- Add support for <bag> and type="configVarying". Some CTS tests use this
  old notation, we need to support it (even though configVarying isn't
  anything supported by the framework convention).

Change-Id: I6946fa633ce513ea8437c1496db883cf27dcf6de
Test: make aapt2_tests
diff --git a/tools/aapt2/Resource_test.cpp b/tools/aapt2/Resource_test.cpp
index 6acb4d3..ad4e3ce 100644
--- a/tools/aapt2/Resource_test.cpp
+++ b/tools/aapt2/Resource_test.cpp
@@ -49,6 +49,10 @@
   ASSERT_NE(type, nullptr);
   EXPECT_EQ(*type, ResourceType::kColor);
 
+  type = ParseResourceType("configVarying");
+  ASSERT_NE(type, nullptr);
+  EXPECT_EQ(*type, ResourceType::kConfigVarying);
+
   type = ParseResourceType("dimen");
   ASSERT_NE(type, nullptr);
   EXPECT_EQ(*type, ResourceType::kDimen);