Add Android sample (JNI binding + Java wrapper class)

[shubham0204]

This PR adds examples/clip.android, an Android sample that interfaces with the shared libraries of clip.cpp through JNI. The structure of the project is highly inspired from llama.cpp/examples/llama.android.

Summary of changes

• examples/clip.android is an Android project with two modules app and clip.
• The app module contains the sources for a demo application which allows the user to select an image and enter a text description to compare them (uses Kotlin/Compose)
• The clip module contains clip/src/main/cpp/clip-android that contains the JNI interfaces which allow communication with the underlying functions from clip.h.
• Also, the clip module contains clip/src/main/java/android/clip/cpp/CLIPAndroid.java which is wrapper class containing native methods.
• The clip module also houses an instrumented test clip/src/androidTest/java/android/example/clip/CLIPInstrumentedTest.kt written in Kotlin
• A README.md is included in the examples/clip.android directory which describes how to run the sample app and the instrumented test
• clip.cpp is modified to address issue (Possible) Incorrect assignment of image mean/std values in clip_model_load() #99
• CMakeLists.txt is modified to add -mcpu=native when ${CMAKE_SYSTEM_PROCESSOR} MATCHES "aarch64" only if -DCLIP_NATIVE is enabled
• added a new method clip_image_preprocess_no_resize in clip.h and clip.cpp which does works exactly like clip_image_preprocess but does not perform linear interpolation (no image resizing). Android's Bitmap class and Python's PIL can handle bilinear interpolation easily, so it would be great to have a method that skips resizing.

Note

Though the clip module here in built as an Android library module, it can be built into a 'Java library' module (packaged as a JAR) and used in other Java-only projects as a port to clip.cpp

It was fun working on this sample, and I would like @monatis to review it and share feedback.