libsnapshot: Refactor code

Move all files related to libsnapshot_cow library to
a seperate directory. Libsnapshot directory is getting
crowded and we will be adding more files to this library
with async writes.

No changes to any logic.

Bug: 254188450
Test: Full OTA on Pixel
Signed-off-by: Akilesh Kailash <akailash@google.com>
Change-Id: If84ff730d477c85a8ef57864d2185f2f897cf8e0

fs_mgr/libsnapshot/Android.bp

@@ -173,10 +173,10 @@ cc_library_static {
         "libsnapshot_cow_defaults",
     ],
     srcs: [
-        "cow_decompress.cpp",
-        "cow_reader.cpp",
-        "cow_writer.cpp",
-        "cow_format.cpp",
+        "libsnapshot_cow/cow_decompress.cpp",
+        "libsnapshot_cow/cow_reader.cpp",
+        "libsnapshot_cow/cow_writer.cpp",
+        "libsnapshot_cow/cow_format.cpp",
     ],
     host_supported: true,
     recovery_available: true,
@@ -424,7 +424,7 @@ cc_test {
         "libsnapshot_cow_defaults",
     ],
     srcs: [
-        "cow_api_test.cpp",
+        "libsnapshot_cow/cow_api_test.cpp",
     ],
     cflags: [
         "-D_FILE_OFFSET_BITS=64",
@@ -546,7 +546,7 @@ cc_binary {
     shared_libs: [
     ],
     srcs: [
-        "inspect_cow.cpp",
+        "libsnapshot_cow/inspect_cow.cpp",
     ],
 }