LibUnicode: Move GenerateUnicodeData's Alias struct to generator header

This will be used for locale aliases as well. Also rename the "property"
field in this struct to "name", as it no longer is only used for
property aliases.

Meta/Lagom/Tools/CodeGenerators/LibUnicode/GenerateUnicodeData.cpp

@@ -45,12 +45,6 @@ struct SpecialCasing {
 // Property descriptions: https://www.unicode.org/reports/tr44/tr44-13.html#PropList.txt
 using PropList = HashMap<String, Vector<CodePointRange>>;
 
-// PropertyAliases source: https://www.unicode.org/Public/13.0.0/ucd/PropertyAliases.txt
-struct Alias {
-    String property;
-    String alias;
-};
-
 // Normalization source: https://www.unicode.org/Public/13.0.0/ucd/DerivedNormalizationProps.txt
 // Normalization descriptions: https://www.unicode.org/reports/tr44/#DerivedNormalizationProps.txt
 enum class QuickCheck {
@@ -479,7 +473,7 @@ enum class @name@ : @underlying@ {)~~~");
 
         for (auto const& alias : aliases) {
             generator.set("alias", alias.alias);
-            generator.set("value", alias.property);
+            generator.set("value", alias.name);
             generator.append(R"~~~(
     @alias@ = @value@,)~~~");
         }
@@ -929,7 +923,7 @@ static void normalize_script_extensions(PropList& script_extensions, PropList co
 
     for (auto const& extension : extensions) {
         auto it = find_if(script_aliases.begin(), script_aliases.end(), [&](auto const& alias) { return extension.key == alias.alias; });
-        auto const& key = (it == script_aliases.end()) ? extension.key : it->property;
+        auto const& key = (it == script_aliases.end()) ? extension.key : it->name;
 
         auto& code_points = script_extensions.find(key)->value;
         code_points.extend(extension.value);

Meta/Lagom/Tools/CodeGenerators/LibUnicode/GeneratorUtil.h

@@ -91,6 +91,11 @@ private:
     HashMap<StringView, StringIndexType> m_unique_string_indices;
 };
 
+struct Alias {
+    String name;
+    String alias;
+};
+
 template<typename StringIndexType>
 struct CanonicalLanguageID {
     static Optional<CanonicalLanguageID> parse(UniqueStringStorage<StringIndexType>& unique_strings, StringView language)