Consolidates the code to find all changed file paths into the `PackageLoopingCommand` class that is the base of almost all of the repo tooling commands. This in a preparatory PR for a future change to allow each command to define a list of files or file patterns that definitively *don't* affect that test, so that CI can be smarter about what tests to run (e.g., not running expensive integration tests for README changes).
A side effect of this change is that tests of almost all commands now need a mock `GitDir` instance. This would add a lot of copy/pasted boilerplate to the test setup, and there is already too much of that, so instead this refactors common test setup:
- Creating a memory file system
- Populating it with a packages directory
- Creating a RecordingProcessRunner to mock out process calls
- Creating a mock GitDir that forwards to a RecordingProcessRunner
into a helper method (using records and destructuring to easily return multiple values). While some tests don't need all of these steps, those that don't can easily ignore parts of it, and it will make it much easier to update tests in the future if they need them, and it makes the setup much more consistent which makes it easier to reason about test setup in general.
Prep for https://github.com/flutter/flutter/issues/136394
Part of fix for https://github.com/flutter/flutter/issues/138336 by bumping the Gradle version of all package example apps (plus `image_picker_android` plugin) to 7.6.3 from those that had a version below that to fix security vulnerability.
Also fixes a bug I found while using the `update-dependencies` packages tool command that caused it to not catch all of the `gradle-wrapper.properties` files when running with the `gradle` dependency + added a test for the fix.
Adds an `android-dependency` option to the `update-dependency` command such that you can update Android dependencies provided the dependency and a version across relevant plugins. This PR specifically adds support for the Gradle dependency, relevant to plugin example apps.
Running the command looks like:
```
dart run script/tool/bin/flutter_plugin_tools.dart update-dependency --android-dependency gradle --version 1.2.3
```
Extracts common logic for running `pub get`, and switches commands to use it. The common logic always uses `flutter pub get` for Flutter packages, rather than `dart pub get`, since the latter will fail if someone has a non-Flutter `dart` in their path before `flutter` (e.g., Dart team members contributing PRs).
