Move Android example to its own package (#6759)

# Objective

- Fix CI issue with updated `cargo-app`

## Solution

- Move the Android example to its own package. It's not necessary for the CI fix, but it's cleaner, mimic the iOS example, and easier to reuse for someone wanting to setup android support in their project
- Build the package in CI instead of the example


The Android example is still working on my android device with this change 👍

.github/workflows/validation-jobs.yml

@@ -54,7 +54,7 @@ jobs:
         run: cargo install --force cargo-apk
 
       - name: Build APK
-        run: ANDROID_NDK_ROOT=$ANDROID_NDK_LATEST_HOME cargo apk build --example android_example
+        run: ANDROID_NDK_ROOT=$ANDROID_NDK_LATEST_HOME cargo apk build --package bevy-android-example
 
   run-examples-on-windows-dx12:
     runs-on: windows-latest

Cargo.toml

@@ -15,6 +15,7 @@ repository = "https://github.com/bevyengine/bevy"
 exclude = ["benches", "crates/bevy_ecs_compile_fail_tests"]
 members = [
   "crates/*",
+  "examples/android",
   "examples/ios",
   "tools/ci",
   "tools/spancmp",
@@ -1587,29 +1588,6 @@ description = "Demonstrates resizing and responding to resizing a window"
 category = "Window"
 wasm = true
 
-# Android
-[[example]]
-crate-type = ["cdylib"]
-name = "android_example"
-path = "examples/android/android.rs"
-
-[package.metadata.example.android_example]
-hidden = true
-
-[package.metadata.android]
-package = "org.bevyengine.example"
-apk_name = "bevyexample"
-assets = "assets"
-resources = "assets/android-res"
-build_targets = ["aarch64-linux-android", "armv7-linux-androideabi"]
-
-[package.metadata.android.sdk]
-target_sdk_version = 31
-
-[package.metadata.android.application]
-icon = "@mipmap/ic_launcher"
-label = "Bevy Example"
-
 [profile.wasm-release]
 inherits = "release"
 opt-level = "z"

examples/android/Cargo.toml

@@ -0,0 +1,29 @@
+[package]
+name = "bevy-android-example"
+version = "0.1.0"
+edition = "2021"
+description = "Example for building an Android app with Bevy"
+publish = false
+license = "MIT OR Apache-2.0"
+
+[lib]
+name = "bevy_android_example"
+crate-type = ["cdylib"]
+
+[dependencies]
+bevy = { path = "../../" }
+
+[package.metadata.android]
+package = "org.bevyengine.example"
+apk_name = "bevyexample"
+assets = "../../assets"
+resources = "../../assets/android-res"
+build_targets = ["aarch64-linux-android", "armv7-linux-androideabi"]
+
+[package.metadata.android.sdk]
+target_sdk_version = 31
+
+[package.metadata.android.application]
+icon = "@mipmap/ic_launcher"
+label = "Bevy Example"
+