treewide: redo handling of kanjidic radicals

lib/models/kanji_search/kanji_search_radical.dart

@@ -4,37 +4,48 @@ class KanjiSearchRadical extends Equatable {
   /// The radical symbol.
   final String symbol;
 
+  /// The names of this radical.
+  ///
+  /// Each name might refer to a specific form of the radical.
+  final List<String> names;
+
   /// The radical forms used in this kanji.
+  ///
+  /// (e.g. "亻" for "人", "氵" for "水")
   final List<String> forms;
 
-  /// The meaning of the radical.
-  final String meaning;
+  /// The meanings of the radical.
+  final List<String> meanings;
 
   // ignore: public_member_api_docs
   const KanjiSearchRadical({
     required this.symbol,
-    this.forms = const [],
-    required this.meaning,
+    required this.names,
+    required this.forms,
+    required this.meanings,
   });
 
   @override
   List<Object> get props => [
         symbol,
+        this.names,
         forms,
-        meaning,
+        meanings,
       ];
 
   Map<String, dynamic> toJson() => {
         'symbol': symbol,
+        'names': names,
         'forms': forms,
-        'meaning': meaning,
+        'meanings': meanings,
       };
 
   factory KanjiSearchRadical.fromJson(Map<String, dynamic> json) {
     return KanjiSearchRadical(
       symbol: json['symbol'] as String,
+      names: (json['names'] as List).map((e) => e as String).toList(),
       forms: (json['forms'] as List).map((e) => e as String).toList(),
-      meaning: json['meaning'] as String,
+      meanings: (json['meanings'] as List).map((e) => e as String).toList(),
     );
   }
 }

lib/models/kanji_search/kanji_search_result.dart

@@ -49,17 +49,17 @@ class KanjiSearchResult extends Equatable {
 
   const KanjiSearchResult({
     required this.kanji,
-    this.taughtIn,
-    this.jlptLevel,
-    this.newspaperFrequencyRank,
+    required this.taughtIn,
+    required this.jlptLevel,
+    required this.newspaperFrequencyRank,
     required this.strokeCount,
     required this.meanings,
-    this.kunyomi = const [],
-    this.onyomi = const [],
+    required this.kunyomi,
+    required this.onyomi,
     // this.kunyomiExamples = const [],
     // this.onyomiExamples = const [],
-    this.radical,
-    this.parts = const [],
+    required this.radical,
+    required this.parts,
     required this.codepoints,
   });