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.cpp b/tools/aapt2/Resource.cpp
index fdabce1..35971e7 100644
--- a/tools/aapt2/Resource.cpp
+++ b/tools/aapt2/Resource.cpp
@@ -39,6 +39,8 @@
       return "bool";
     case ResourceType::kColor:
       return "color";
+    case ResourceType::kConfigVarying:
+      return "configVarying";
     case ResourceType::kDimen:
       return "dimen";
     case ResourceType::kDrawable:
@@ -85,6 +87,7 @@
     {"^attr-private", ResourceType::kAttrPrivate},
     {"bool", ResourceType::kBool},
     {"color", ResourceType::kColor},
+    {"configVarying", ResourceType::kConfigVarying},
     {"dimen", ResourceType::kDimen},
     {"drawable", ResourceType::kDrawable},
     {"font", ResourceType::kFont},