Add FuseAppLoop to libappfuse.

The class is used at the app side (StorageManager) to parse FUSE
commands.

Bug: 32260320
Test: libappfuse_test
Change-Id: I1ae2904d3290a041f1efbf8fc10ba032eda5449c
diff --git a/libappfuse/tests/FuseBufferTest.cc b/libappfuse/tests/FuseBufferTest.cc
index 1aacfe3..17f1306 100644
--- a/libappfuse/tests/FuseBufferTest.cc
+++ b/libappfuse/tests/FuseBufferTest.cc
@@ -24,6 +24,7 @@
 #include <gtest/gtest.h>
 
 namespace android {
+namespace fuse {
 
 constexpr char kTempFile[] = "/data/local/tmp/appfuse_test_dump";
 
@@ -183,5 +184,6 @@
   ASSERT_EQ(sizeof(fuse_out_header), buffer.response.header.len);
   EXPECT_EQ(-ENOSYS, buffer.response.header.error);
 }
-}
-  // namespace android
+
+} // namespace fuse
+} // namespace android