Add golden tests for systemfeatures codegen

Add a simple golden test suite for systemfeature codegen. This can be
run via atest, or as a standalone script. The golden sources can be
updated via:

  ./frameworks/base/tools/systemfeatures/tests/golden_test.sh --update

Test: atest systemfeatures-gen-golden-tests
Bug: 203143243
Flag: NA

Change-Id: Iacb9558617845132ccfffbae34c333d39c84c065
diff --git a/tools/systemfeatures/tests/golden/RwNoFeatures.java.gen b/tools/systemfeatures/tests/golden/RwNoFeatures.java.gen
new file mode 100644
index 0000000..2111d56
--- /dev/null
+++ b/tools/systemfeatures/tests/golden/RwNoFeatures.java.gen
@@ -0,0 +1,24 @@
+// This file is auto-generated. DO NOT MODIFY.
+// Args: com.android.systemfeatures.RwNoFeatures \
+//            --readonly=false
+package com.android.systemfeatures;
+
+import android.annotation.Nullable;
+import android.content.Context;
+
+/**
+ * @hide
+ */
+public final class RwNoFeatures {
+    private static boolean hasFeatureFallback(Context context, String featureName) {
+        return context.getPackageManager().hasSystemFeature(featureName, 0);
+    }
+
+    /**
+     * @hide
+     */
+    @Nullable
+    public static Boolean maybeHasFeature(String featureName, int version) {
+        return null;
+    }
+}