Update agdk-mainloop

- Renames package to com.github.rust_mobile.agdkmainloop
- Updates Gradle / AGP
- Updates icon
- Addresses various deprecation warnings
- Adds .vscode/settings.json to specify aarch64-linux-android target

Author: rib

agdk-mainloop/.vscode/settings.json

@@ -0,0 +1,7 @@
+{
+    "rust-analyzer.cargo.target": "aarch64-linux-android",
+    "editor.formatOnSave": true,
+    "[xml]": {
+        "editor.formatOnSave": false
+    }
+}