Repository: flutter
Issue: [tool] New project gitignore still defines rules for Android and iOS folder, instead of placing them in the Android/iOS gitignore file 
Labels: tool,c: proposal,P3,team-tool,triaged-tool

### Use case

Users creating a new Flutter project that want to benefit from the starting gitignore.

### Proposal

Currently when creating a new Flutter project, most of the Android & iOS specific things are split off into their own gitignores in the Android & iOS directories.

However, this isn't the case for all the rules.

For iOS, we still define `**/ios/Flutter/.last_build_id` in the root gitignore at https://github.com/flutter/flutter/blob/master/packages/flutter_tools/templates/app_shared/.gitignore.tmpl#L28

For Android, we still define 
```
/android/app/debug
/android/app/profile
/android/app/release
```

at the bottom of the same template.

We should probably move these gitignore lines into their Android / iOS specific counterparts.

Steps to reproduce:
1. `flutter create sample`
2. `cd sample && cat .gitignore`
3. The `ios` and `android` folders are still present in rules in that file

Question: I'm not sure if the `**/` glob pattern is for add-to-app use cases?

<details>

  <summary>Flutter Doctor</summary>
  
  ```console
[✓] Flutter (Channel stable, 3.24.1, on macOS 14.6.1 23G93 darwin-x64, locale en-BE)
    • Flutter version 3.24.1 on channel stable at /Users/navaronbracke/Documents/flutter
    • Upstream repository git@github.com:navaronbracke/flutter.git
    • FLUTTER_GIT_URL = git@github.com:navaronbracke/flutter.git
    • Framework revision 5874a72aa4 (6 days ago), 2024-08-20 16:46:00 -0500
    • Engine revision c9b9d5780d
    • Dart version 3.5.1
    • DevTools version 2.37.2

[✓] Android toolchain - develop for Android devices (Android SDK version 34.0.0)
    • Android SDK at /Users/navaronbracke/Library/Android/sdk
    • Platform android-34, build-tools 34.0.0
    • ANDROID_HOME = /Users/navaronbracke/Library/Android/sdk
    • Java binary at: /Applications/Android Studio.app/Contents/jbr/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build 17.0.10+0-17.0.10b1087.21-11572160)
    • All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 15.4)
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Build 15F31d
    • CocoaPods version 1.15.2

[✓] Chrome - develop for the web
    • Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome

[✓] Android Studio (version 2023.3)
    • Android Studio at /Applications/Android Studio.app/Contents
    • Flutter plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/9212-flutter
    • Dart plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/6351-dart
    • Java version OpenJDK Runtime Environment (build 17.0.10+0-17.0.10b1087.21-11572160)

[✓] VS Code (version 1.92.2)
    • VS Code at /Applications/Visual Studio Code.app/Contents
    • Flutter extension version 3.94.0

[✓] Connected device (2 available)
    • macOS (desktop) • macos  • darwin-x64     • macOS 14.6.1 23G93 darwin-x64
    • Chrome (web)    • chrome • web-javascript • Google Chrome 128.0.6613.85

[✓] Network resources
    • All expected network resources are available.

• No issues found!
```

</details>