Bump to Android 35 (#870)

**DO NOT LAND YET:** Please review flutter/engine#53574 first; will merge this once it is approved.

Change engine to use Android 15.

Buildroot step of https://github.com/flutter/flutter/blob/master/docs/platforms/android/Upgrading-Engine's-Android-API-version.md to complete flutter/flutter#150215.

build/config/android/config.gni

@@ -7,8 +7,8 @@
 if (is_android) {
   if (!defined(default_android_sdk_root)) {
     default_android_sdk_root = "//flutter/third_party/android_tools/sdk"
-    default_android_sdk_version = "34"
-    default_android_sdk_build_tools_version = "34.0.0"
+    default_android_sdk_version = "35"
+    default_android_sdk_build_tools_version = "35.0.0-rc4"
   }
 
   declare_args() {