Update examples

This updates both the examples to Gradle 9 and AGP 9.1

The examples are identical, except that `na-mainloop` is based on
NativeActivity and the `agdk-mainloop` based on GameActivity.

The examples demonstrate:
- Using the `jni` API to define enough bindings to be able to send a Toast
- Using an `android_on_create` entry point for logging initialization
  and JNI initialization
- Using `AndroidApp::run_on_java_main_thread()` to send a toast from the
  Java main / UI thread
- Running an `android_main` event loop, including printing historic
  pointer samples (a new 0.6.1 feature)

The examples support two input actions:
- Lifting your finger in the top-left corner of the screen will show the
  onscreen keyboard
- Lifting your finger in the top-right corner of the screen will hide
  the onscreen keyboard

If you edit and disable `configChanges` in `AndroidManifest.xml` then
these examples can also demonstrate that `android-activity` gracefully
handles repeated `Activity` create -> run -> destroy cycles.

Author: rib

examples/agdk-mainloop/.gitignore

@@ -1,8 +1,8 @@
 *.iml
-.idea
 .gradle
 /local.properties
 /.idea
+/.vscode
 .DS_Store
 /build
 /captures