Repository: flutter
Issue: HTTP Validator doctor check should report why a failed connection would cause issues
Labels: tool,t: flutter doctor,P3,team-tool,triaged-tool

### Is there an existing issue for this?

- [X] I have searched the [existing issues](https://github.com/flutter/flutter/issues)
- [X] I have read the [guide to filing a bug](https://flutter.dev/docs/resources/bug-reports)

### Steps to reproduce

Behind a corporate firewall --

Run
`flutter doctor -v`

This will eventually timeout and report that https://cocoapods.org/ is not reachable.

But, why should it be reachable. This is not where the CocoaPods spec file exists? What is the significance of checking this URL.

Same might be said for `https://cloud.google.com/`


### Actual results

Flutter Doctor reports

HTTP Host availability check is taking a long time...[!] HTTP Host Availability
    ✗ HTTP host "https://cocoapods.org/" is not reachable. Reason: An error occurred while checking the HTTP host:
      Operation timed out

### Logs

<details>
<summary>Logs</summary>

```console

<!-- Paste your logs here -->

```

</details>


### Flutter Doctor output

<details>
<summary>Doctor output</summary>

```console
[✓] Flutter (Channel stable, 3.7.12, on macOS 13.6.1 22G313 darwin-arm64, locale en-US)
    • Flutter version 3.7.12 on channel stable at /usr/local/jpmc/flutter
    • Upstream repository https://bitbucketdc-cluster07.jpmchase.net/scm/cbcdo/flutter.git
    • FLUTTER_GIT_URL = https://bitbucketdc-cluster07.jpmchase.net/scm/cbcdo/flutter.git
    • Framework revision f4fba29c48 (5 minutes ago), 2023-11-13 11:28:47 -0500
    • Engine revision 1a65d409c7
    • Dart version 2.19.6
    • DevTools version 2.20.1
    • Pub download mirror https://unpub.dev.aws.jpmchase.net
    • Flutter download mirror http://localhost:3000

[✓] Android toolchain - develop for Android devices (Android SDK version 34.0.0)
    • Android SDK at /Users/r610031/Library/Android/sdk
    • Platform android-34, build-tools 34.0.0
    • Java binary at: /Applications/Android Studio.app/Contents/jbr/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build 17.0.6+0-17.0.6b829.9-10027231)
    • All Android licenses accepted.

[!] Xcode - develop for iOS and macOS (Xcode 14.3.1)
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Build 14E300c
    ✗ CocoaPods not installed.
        CocoaPods is used to retrieve the iOS and macOS platform side's plugin code that responds to your plugin usage on
        the Dart side.
        Without CocoaPods, plugins will not work on iOS or macOS.
        For more info, see https://flutter.dev/platform-plugins
      To install see https://guides.cocoapods.org/using/getting-started.html#installation for instructions.

[✓] Chrome - develop for the web
    • Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome

[✓] Android Studio (version 2022.3)
    • 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 17.0.6+0-17.0.6b829.9-10027231)

[✓] IntelliJ IDEA Ultimate Edition (version 2023.2)
    • IntelliJ at /Applications/IntelliJ IDEA.app
    • Flutter plugin version 75.1.4
    • Dart plugin version 232.8660.129

[✓] VS Code (version 1.81.1)
    • VS Code at /Applications/Visual Studio Code.app/Contents
    • Flutter extension version 3.74.0

[✓] Connected device (2 available)
    • macOS (desktop) • macos  • darwin-arm64   • macOS 13.6.1 22G313 darwin-arm64
    • Chrome (web)    • chrome • web-javascript • Google Chrome 119.0.6045.105

HTTP Host availability check is taking a long time...[!] HTTP Host Availability
    ✗ HTTP host "https://cocoapods.org/" is not reachable. Reason: An error occurred while checking the HTTP host:
      Operation timed out
```

</details>