Fix shorebird_ci

[bryanoltman]

Updates the checkout action to fetch all branches and tags, which is required to determine Flutter version.

Note: regular CI still seems to be broken for an unrelated reason.

The problem we're seeing is in https://github.com/shorebirdtech/flutter/actions/runs/9196867990/job/25295975746, where our tests fail with the following:

Exception: Failed to create Flutter project: Downloading Linux x64 Dart SDK from Flutter engine 9f5711d6916088b4caf07badb1aef01b600eff3c...
  Building flutter tool...
  Flutter assets will be downloaded from https://download.shorebird.dev./ Make sure you trust this source!
  Note: leak_tracker_flutter_testing is pinned to version 3.0.3 by flutter_test from the flutter SDK.
  See https://dart.dev/go/sdk-version-pinning for details.
  
  The current Flutter SDK version is 0.0.0-unknown.
  
  Because every version of flutter_test from sdk depends on leak_tracker_flutter_testing >=2.0.3 which requires Flutter SDK version >=3.[18](https://github.com/shorebirdtech/flutter/actions/runs/9196867990/job/25295975746#step:5:19).0-18.0.pre.54, flutter_test from sdk is forbidden.
  So, because shorebird_test depends on flutter_test from sdk, version solving failed.
  
  
  You can try the following suggestion to make the pubspec resolve:
  * Try using the Flutter SDK version: 3.22.0. 
  
  test/shorebird_tests.dart 47:5  _createFlutterProject
  ===== asynchronous gap ===========================
  test/shorebird_tests.dart 75:9  testWithShorebirdProject.<fn>

I'm able to reproduce this by following the same steps as the checkout action.

Proof of fix: https://github.com/shorebirdtech/flutter/actions/runs/9197333224

[eseidel]

What about just "fetch-tags" instead of fetch-depth: 0?

[eseidel]

Or do we specifically need branches?

[eseidel]

https://github.com/actions/checkout

[bryanoltman]

I tried with fetch-tags and that didn't seem to change the version detection issue ¯_(ツ)_/¯

[eseidel]

Thanks for trying!