- Updates the remaining tests (other than one that still needs to be
converted to the new base command, which will be fixed then) that
aren't using runCapturingPrint to do so to reduce test log spam.
- Simplifies and standardizes the matcher used for ToolExit in tests.
Combines the two different aspects of version-checking into a single looping structure based on plugins, using the new base command, rather than one operating on plugins as controlled by the usual flags and the other operating on a git list of changed files.
Also simplifies the determination of the new version by simply checking the file, rather than querying git for the HEAD state of the file. Tests setup is simplified since we no longer need to set up nearly as much fake `git` output.
Minor changes to base commands:
- Move indentation up to PackageLoopingCommand so that it is consistent across commands
- Add a new post-loop command for any cleanup, which is needed by version-check
- Change the way the GitDir instance is managed by the base PluginCommand, so that it's always cached even when not overridden, to reduce duplicate work and code.
Part of https://github.com/flutter/flutter/issues/83413
