Eliminate build_all_plugins_app.sh (#4232)

Removes the `build_all_plugins_app.sh` bash script, in support of the goal of eliminating all use of bash from the repository (for maintainability, and for better Windows compatibility).

- The exclusion list moves to a config file, match other recent repo changes
- The exclusion logging moves into the tool itself, consistent with the tool doing more logging of skipped and excluded plugins
- The bulk of the logic moves to a Cirrus task template. This was done instead of rewriting the script in Dart, even though it will mean more work for alternate CI support (e.g., bringing this up on a Windows LUCI bot), because breaking it into components makes it easier to pinpoint failures from the CI UI rather than having all the steps smashed together.

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

@@ -191,7 +191,7 @@ abstract class PluginCommand extends Command<void> {
   }
 
   /// Returns the set of plugins to exclude based on the `--exclude` argument.
-  Set<String> _getExcludedPackageName() {
+  Set<String> getExcludedPackageNames() {
     final Set<String> excludedPackages = _excludedPackages ??
         getStringListArg(_excludeArg).expand<String>((String item) {
           if (item.endsWith('.yaml')) {
@@ -265,7 +265,7 @@ abstract class PluginCommand extends Command<void> {
   Stream<PackageEnumerationEntry> _getAllPackages() async* {
     Set<String> plugins = Set<String>.from(getStringListArg(_packagesArg));
 
-    final Set<String> excludedPluginNames = _getExcludedPackageName();
+    final Set<String> excludedPluginNames = getExcludedPackageNames();
 
     final bool runOnChangedPackages = getBoolArg(_runOnChangedPackagesArg);
     if (plugins.isEmpty &&