LibJS+LibUnicode: Don't remove {currency} keys in GetNumberFormatPattern

In order to implement Intl.NumberFormat.prototype.formatToParts, do not
replace {currency} keys in the format pattern before ECMA-402 tells us
to. Otherwise, the array return by formatToParts will not contain the
expected currency key.

Early replacement was done to avoid resolving the currency display more
than once, as it involves a couple of round trips to search through
LibUnicode data. So this adds a non-standard method to NumberFormat to
do this resolution and cache the result.

Another side effect of this change is that LibUnicode must replace unit
format patterns of the form "{0} {1}" during code generation. These were
previously skipped during code generation because LibJS would just
replace the keys with the currency display at runtime. But now that the
currency display injection is delayed, any {0} or {1} keys in the format
pattern will cause PartitionNumberPattern to abort.

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

@@ -79,24 +79,23 @@ struct UnicodeLocaleData {
     Vector<String> numeric_symbols;
 };
 
-static void parse_number_pattern(String pattern, UnicodeLocaleData& locale_data, NumberFormat& format, bool is_unit_pattern = false)
+static void parse_number_pattern(String pattern, UnicodeLocaleData& locale_data, NumberFormat& format)
 {
     // https://unicode.org/reports/tr35/tr35-numbers.html#Number_Format_Patterns
     // https://cldr.unicode.org/translation/number-currency-formats/number-and-currency-patterns
     auto replace_patterns = [&](String pattern) {
-        if (is_unit_pattern) {
-            // Skip parsing unit patterns, which are of the form "{0} {1}", and do not contain any
-            // of the replacement patterns below.
-            return pattern;
-        }
-
         static HashMap<StringView, StringView> replacements = {
+            { "{0}"sv, "{number}"sv },
+            { "{1}"sv, "{currency}"sv },
             { "%"sv, "{percentSign}"sv },
             { "+"sv, "{plusSign}"sv },
             { "-"sv, "{minusSign}"sv },
             { "¤"sv, "{currency}"sv }, // U+00A4 Currency Sign
         };
 
+        for (auto const& replacement : replacements)
+            pattern = pattern.replace(replacement.key, replacement.value, true);
+
         if (auto start_number_index = pattern.find_any_of("#0"sv, String::SearchDirection::Forward); start_number_index.has_value()) {
             auto end_number_index = *start_number_index + 1;
 
@@ -111,9 +110,6 @@ static void parse_number_pattern(String pattern, UnicodeLocaleData& locale_data,
                 pattern.substring_view(end_number_index));
         }
 
-        for (auto const& replacement : replacements)
-            pattern = pattern.replace(replacement.key, replacement.value, true);
-
         return pattern;
     };
 
@@ -173,18 +169,16 @@ static void parse_number_systems(String locale_numbers_path, UnicodeLocaleData&
                 return;
 
             NumberFormat format {};
-            bool is_unit_pattern = false;
 
             if (auto type = split_key[0].template to_uint<u64>(); type.has_value()) {
                 VERIFY(*type % 10 == 0);
                 format.magnitude = static_cast<u8>(log10(*type));
             } else {
                 VERIFY(split_key[0] == "unitPattern"sv);
-                is_unit_pattern = true;
             }
 
             format.plurality = NumberFormat::plurality_from_string(split_key[2]);
-            parse_number_pattern(value.as_string(), locale_data, format, is_unit_pattern);
+            parse_number_pattern(value.as_string(), locale_data, format);
 
             result.append(move(format));
         });