[libmotionphoto] Promote Development to main (HEIC/AVIF detection without libheif & extractor decoupling)

[DichenZhang1]

Summary

Promotes Development (b09d29d) into main, bringing in:

1. PR Decouple Motion Photo extractor from MotionPhotoChecker and track exact video/image offsets #7 (562d71f) — Decouple Motion Photo extractor from MotionPhotoChecker and track exact video/image offsets:

   • Splits ParseXmpMetadata() out of ParseAndCheckXmpMetadata() in motion_photo_checker_extractor_common.{h,cc}.
   • Removes MotionPhotoChecker calls from ExtractMotionPhoto in motion_photo_extractor/function.cc and guards the 3P MetadataEngine extraction fast-path with engine.IsMotionPhoto(collection).
   • Adds ExtractionBypassesCheckerValidation unit test in motion_photo_extractor_test.cc.

2. PR fix(heif): detect HEIC and AVIF motion photos without libheif #8 (b09d29d) — Detect HEIC and AVIF motion photos without libheif:

   • Adds libheif-free CreateHeifContainerSplitter() in heif_container_splitter.cc (container_splitter.h, jpeg_container_splitter.cc, metadata_engine.cc).
   • Adds SniffFileType() in motion_photo_jni.cc so JNI parseMetadata / parseMetadataFd and AGTM entry points detect ftyp HEIC/AVIF inputs.
   • Adds unit tests in heif_container_splitter_test.cc, libmotionphoto_api_test.cc, and MetadataEngineTest.java.

Verification

• Standalone CMake build & test (./build.sh && ./test.sh): 74/74 tests passed
• API doc check (./tools/check_api_doc.sh): Passed
• Google3 Blaze C++ & Robolectric test suites: 15/15 test suites passed
• Android arm64-v8a JNI build: Passed