android : introduce starter project example (#4926)

* Introduce starter project for Android

Based on examples/llama.swiftui.

* Add github workflow

* Set NDK version

* Only build arm64-v8a in CI

* Sync bench code

* Rename CI prop to skip-armeabi-v7a

* Remove unused tests

examples/llama.android/.gitignore

@@ -0,0 +1,33 @@
+# Gradle files
+.gradle/
+build/
+
+# Local configuration file (sdk path, etc)
+local.properties
+
+# Log/OS Files
+*.log
+
+# Android Studio generated files and folders
+captures/
+.externalNativeBuild/
+.cxx/
+*.apk
+output.json
+
+# IntelliJ
+*.iml
+.idea/
+misc.xml
+deploymentTargetDropDown.xml
+render.experimental.xml
+
+# Keystore files
+*.jks
+*.keystore
+
+# Google Services (e.g. APIs or Firebase)
+google-services.json
+
+# Android Profiling
+*.hprof