[flutter_plugin_tool] Migrate 'publish' to new base command

[stuartmorgan]

Moves publish to PackageLoopingCommand, giving it the same
standardized output and summary that is used by most other commands in
the tool.

Adds minor new functionality to the base command to allow it to handle
the specific needs of publish:

• Allows fully customizing the set of packages to loop over, to support
  --all-changed
• Allows customization of a few more strings so the output better
  matches the functionality (e.g., using 'published' instead of 'ran' in
  the summary lines).

Fixes flutter/flutter#83413

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.

[cyanglaz]

LGTM