switch expressions: finale (#148711)

### fixes #136139

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<details open> <summary><b>getting sentimental in the PR description</b> (click to collapse)<br><br></summary>

The past 7 months have been quite the journey—I made some huge blunders and some huge accomplishments—a very fun time overall.

I really appreciate the people who took the time to perform code review for my refactoring shenanigans: **christopherfujino**, **andrewkolos**, **LongCatIsLooong**, **gspencergoog**, **loic-sharma**, **Piinks**, **bernaferrari**, **bartekpacia**, **bleroux**, **kevmoo**, **rakudrama**, **XilaiZhang**, **QuncCccccc**, **MominRaza**, and **victorsanni**.

And a huge shoutout to 2 individuals:
- @justinmc, for offering to sponsor me for commit access (words could not describe my excitement)
- @goderbauer, for being super duper proactive and consistent with code review

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</details>

This pull request makes 13 "switch statements → switch expressions" PRs in total, reducing the LOC in this repo by **1,974**!

From now on, I'll make sure to request a test exemption for each refactoring PR 🙂

dev/tools/localization/bin/gen_localizations.dart

@@ -400,17 +400,12 @@ $factoryDeclaration
 ///
 /// Used by [generateGetter] below.
 String generateType(Map<String, dynamic>? attributes) {
-  bool optional = false;
-  String type = 'String';
-  if (attributes != null) {
-    optional = attributes.containsKey('optional');
-    switch (attributes['x-flutter-type'] as String?) {
-      case 'icuShortTimePattern':
-        type = 'TimeOfDayFormat';
-      case 'scriptCategory':
-        type = 'ScriptCategory';
-    }
-  }
+  final bool optional = attributes?.containsKey('optional') ?? false;
+  final String type = switch (attributes?['x-flutter-type']) {
+    'icuShortTimePattern' => 'TimeOfDayFormat',
+    'scriptCategory' => 'ScriptCategory',
+    _ => 'String',
+  };
   return type + (optional ? '?' : '');
 }