[flutter_plugin_tools] Improve license-check output

[stuartmorgan-g]

Currently each type of check handles its output in isolation, which
creates confusing output when the last check succeeds but an earlier
check fails, since the end of the output will just be a success message.

This makes the output follow the same basic approach as the package
looper commands, where all failures are collected, and then a final
summary is presented at the end, so the last message will always reflect
the important details.

It also adopts the colorized output now used by most other commands.

Pre-launch Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene wiki page, which explains my responsibilities.
• I read and followed the relevant style guides and ran the auto-formatter. (Note that unlike the flutter/flutter repo, the flutter/plugins repo does use dart format.)
• I signed the CLA.
• The title of the PR starts with the name of the plugin surrounded by square brackets, e.g. [shared_preferences]
• I listed at least one issue that this PR fixes in the description above.
• I updated pubspec.yaml with an appropriate new version according to the pub versioning philosophy.
• I updated CHANGELOG.md to add a description of the change.
• I updated/added relevant documentation (doc comments with ///).
• I added new tests to check the change I am making or feature I am adding, or Hixie said the PR is test exempt.
• All existing and new tests are passing.

[stuartmorgan-g]

The code diff looks worse than it actually is; it's mostly just moving code.

(This is unrelated to the other recent PRs, it's just to address something I saw cause confusion on another PR.)

[ditman]

Very nice!

[ditman]

The code diff looks worse than it actually is; it's mostly just moving code.

Yeah, I noticed this pretty much only handles the return of already existing checks in a slightly different way. Good stuff!

My only comment would be to return a Map<_ReasonForFailure, List<String>> instead of List<File> when validating (return only the path of the failing file), but since you're already passing in a list with all the files, and that function is only filtering, and no new Files are being created, it doesn't matter!

[stuartmorgan-g]

My only comment would be to return a Map<_ReasonForFailure, List<String>> instead of List<File> when validating (return only the path of the failing file), but since you're already passing in a list with all the files, and that function is only filtering, and no new Files are being created, it doesn't matter!

That's actually the signature I wrote when I started reworking the return value, before I realized it was easier in practice to just use File given the structure that was already there. 🙂