Meta: Don't assume how each generator wants to generate keyed map names

The generate_mapping helper generates a series of structs like:

    Array<SomeType, 1> s_mapping_key_0 {};
    Array<SomeType, 2> s_mapping_key_1 {};
    Array<SomeType, 3> s_mapping_key_2 {};
    Array<Span<SomeType const>> s_mapping { {
        s_mapping_key_0.span(),
        s_mapping_key_1.span(),
        s_mapping_key_2.span(),
    } };

Where the names of the struct were generated by the format_mapping_name
lambda inside the helper. Rather than this lambda making assumptions on
how each generator wants to name its structs, add a parameter for the
caller to provide a naming formatter.

This is because the TimeZoneData generator will want pretty specific
identifier formatting rules.

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

@@ -1814,7 +1814,7 @@ static constexpr Array<@type@, @size@> @name@ { {)~~~");
     auto locales = locale_data.locales.keys();
     quick_sort(locales);
 
-    generate_mapping(generator, locale_data.locales, s_calendar_index_type, "s_locale_calendars"sv, "s_calendars_{}", [&](auto const& name, auto const& value) { append_calendars(name, value.calendars); });
+    generate_mapping(generator, locale_data.locales, s_calendar_index_type, "s_locale_calendars"sv, "s_calendars_{}", format_identifier, [&](auto const& name, auto const& value) { append_calendars(name, value.calendars); });
     append_mapping(locales, locale_data.locales, s_time_zone_index_type, "s_locale_time_zones"sv, [](auto const& locale) { return locale.time_zones; });
     append_mapping(locales, locale_data.locales, s_time_zone_format_index_type, "s_locale_time_zone_formats"sv, [](auto const& locale) { return locale.time_zone_formats; });
     append_mapping(locales, locale_data.locales, s_day_period_index_type, "s_locale_day_periods"sv, [](auto const& locale) { return locale.day_periods; });

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

@@ -827,8 +827,8 @@ static constexpr Array<@type@, @size@> @name@ { {)~~~");
         generator.append(" } };");
     };
 
-    generate_mapping(generator, locale_data.locales, s_number_system_index_type, "s_locale_number_systems"sv, "s_number_systems_{}", [&](auto const& name, auto const& value) { append_map(name, s_number_system_index_type, value.number_systems); });
-    generate_mapping(generator, locale_data.locales, s_unit_index_type, "s_locale_units"sv, "s_units_{}", [&](auto const& name, auto const& value) { append_map(name, s_unit_index_type, value.units); });
+    generate_mapping(generator, locale_data.locales, s_number_system_index_type, "s_locale_number_systems"sv, "s_number_systems_{}", nullptr, [&](auto const& name, auto const& value) { append_map(name, s_number_system_index_type, value.number_systems); });
+    generate_mapping(generator, locale_data.locales, s_unit_index_type, "s_locale_units"sv, "s_units_{}", nullptr, [&](auto const& name, auto const& value) { append_map(name, s_unit_index_type, value.units); });
 
     generator.append(R"~~~(
 static NumberSystem const* find_number_system(StringView locale, StringView system)

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

@@ -399,12 +399,18 @@ enum class @name@ : @underlying@ {)~~~");
 )~~~");
 }
 
-template<typename LocalesType, typename ListFormatter>
-void generate_mapping(SourceGenerator& generator, LocalesType const& locales, StringView type, StringView name, StringView format, ListFormatter&& format_list)
+template<typename LocalesType, typename IdentifierFormatter, typename ListFormatter>
+void generate_mapping(SourceGenerator& generator, LocalesType const& locales, StringView type, StringView name, StringView format, IdentifierFormatter&& format_identifier, ListFormatter&& format_list)
 {
-    auto format_mapping_name = [](StringView format, StringView name) {
-        auto mapping_name = name.to_lowercase_string().replace("-"sv, "_"sv, true).replace("/"sv, "_"sv, true);
-        return String::formatted(format, mapping_name);
+    auto format_mapping_name = [&](StringView format, StringView name) {
+        String mapping_name;
+
+        if constexpr (IsNullPointer<IdentifierFormatter>)
+            mapping_name = name.replace("-"sv, "_"sv, true);
+        else
+            mapping_name = format_identifier(type, name);
+
+        return String::formatted(format, mapping_name.to_lowercase());
     };
 
     Vector<String> mapping_names;