[flutter_plugin_tool] Migrate 'publish' to new base command (#4290)

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

Author: stuartmorgan-g

script/tool/lib/src/common/package_looping_command.dart

@@ -92,6 +92,18 @@ abstract class PackageLoopingCommand extends PluginCommand {
   /// arguments are invalid), and to set up any run-level state.
   Future<void> initializeRun() async {}
 
+  /// Returns the packages to process. By default, this returns the packages
+  /// defined by the standard tooling flags and the [inculdeSubpackages] option,
+  /// but can be overridden for custom package enumeration.
+  ///
+  /// Note: Consistent behavior across commands whenever possibel is a goal for
+  /// this tool, so this should be overridden only in rare cases.
+  Stream<PackageEnumerationEntry> getPackagesToProcess() async* {
+    yield* includeSubpackages
+        ? getTargetPackagesAndSubpackages(filterExcluded: false)
+        : getTargetPackages(filterExcluded: false);
+  }
+
   /// Runs the command for [package], returning a list of errors.
   ///
   /// Errors may either be an empty string if there is no context that should
@@ -138,6 +150,9 @@ abstract class PackageLoopingCommand extends PluginCommand {
   /// context.
   String get failureListFooter => 'See above for full details.';
 
+  /// The summary string used for a successful run in the final overview output.
+  String get successSummaryMessage => 'ran';
+
   /// If true, all printing (including the summary) will be redirected to a
   /// buffer, and provided in a call to [handleCapturedOutput] at the end of
   /// the run.
@@ -206,9 +221,8 @@ abstract class PackageLoopingCommand extends PluginCommand {
 
     await initializeRun();
 
-    final List<PackageEnumerationEntry> targetPackages = includeSubpackages
-        ? await getTargetPackagesAndSubpackages(filterExcluded: false).toList()
-        : await getTargetPackages(filterExcluded: false).toList();
+    final List<PackageEnumerationEntry> targetPackages =
+        await getPackagesToProcess().toList();
 
     final Map<PackageEnumerationEntry, PackageResult> results =
         <PackageEnumerationEntry, PackageResult>{};
@@ -346,7 +360,7 @@ abstract class PackageLoopingCommand extends PluginCommand {
         summary = 'skipped';
         style = hadWarning ? Styles.LIGHT_YELLOW : Styles.DARK_GRAY;
       } else {
-        summary = 'ran';
+        summary = successSummaryMessage;
         style = hadWarning ? Styles.YELLOW : Styles.GREEN;
       }
       if (hadWarning) {