AK: Use an enum instead of a bool for String::replace(all_occurences)

This commit has no behavior changes.

In particular, this does not fix any of the wrong uses of the previous
default parameter (which used to be 'false', meaning "only replace the
first occurence in the string"). It simply replaces the default uses by
String::replace(..., ReplaceMode::FirstOnly), leaving them incorrect.

Userland/Libraries/LibUnicode/DateTimeFormat.cpp

@@ -246,7 +246,7 @@ static Optional<String> format_time_zone_offset(StringView locale, CalendarPatte
 
     // The digits used for hours, minutes and seconds fields in this format are the locale's default decimal digits.
     auto result = replace_digits_for_number_system(*number_system, builder.build());
-    return formats->gmt_format.replace("{0}"sv, result);
+    return formats->gmt_format.replace("{0}"sv, result, ReplaceMode::FirstOnly);
 }
 
 // https://unicode.org/reports/tr35/tr35-dates.html#Time_Zone_Format_Terminology

Userland/Libraries/LibUnicode/Locale.cpp

@@ -816,7 +816,7 @@ Optional<String> format_locale_for_display(StringView locale, LocaleID locale_id
     Optional<String> secondary_tag;
 
     if (script.has_value() && region.has_value())
-        secondary_tag = patterns->locale_separator.replace("{0}"sv, *script).replace("{1}"sv, *region);
+        secondary_tag = patterns->locale_separator.replace("{0}"sv, *script, ReplaceMode::FirstOnly).replace("{1}"sv, *region, ReplaceMode::FirstOnly);
     else if (script.has_value())
         secondary_tag = *script;
     else if (region.has_value())
@@ -825,7 +825,7 @@ Optional<String> format_locale_for_display(StringView locale, LocaleID locale_id
     if (!secondary_tag.has_value())
         return primary_tag;
 
-    return patterns->locale_pattern.replace("{0}"sv, primary_tag).replace("{1}"sv, *secondary_tag);
+    return patterns->locale_pattern.replace("{0}"sv, primary_tag, ReplaceMode::FirstOnly).replace("{1}"sv, *secondary_tag, ReplaceMode::FirstOnly);
 }
 
 Optional<ListPatterns> __attribute__((weak)) get_locale_list_patterns(StringView, StringView, Style) { return {}; }

Userland/Libraries/LibUnicode/NumberFormat.cpp

@@ -105,7 +105,7 @@ Optional<String> augment_currency_format_pattern([[maybe_unused]] StringView cur
     }
 
     if (currency_key_with_spacing.has_value())
-        return base_pattern.replace(currency_key, *currency_key_with_spacing);
+        return base_pattern.replace(currency_key, *currency_key_with_spacing, ReplaceMode::FirstOnly);
 #endif
 
     return {};