[Android] Support PPTinyPose on Android (#746)

* [Android] Update ppseg jni via new api and optimize jni vis funcs

* delete local refs

* [Android] Add PPTinyPose jni and java api

* [Android] Update gradle download tasks info

* [Android] Add PPTinyPose Android app example

* update app build.gradle

java/android/ui/build.gradle

@@ -7,6 +7,7 @@ android {
 
     defaultConfig {
         minSdkVersion 15
+        //noinspection ExpiredTargetSdkVersion
         targetSdkVersion 28
         
         testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"