AK+Everywhere: Turn bool keep_empty to an enum in split* functions

Author: https://github.com/demostanis
Commit: 3e8b5ac920
Pull-request: https://github.com/SerenityOS/serenity/pull/15750
Reviewed-by: https://github.com/AtkinsSJ
Reviewed-by: https://github.com/davidot
Reviewed-by: https://github.com/linusg ✅

Userland/Libraries/LibC/getopt.cpp

@@ -138,7 +138,7 @@ int OptionParser::getopt()
 
 bool OptionParser::lookup_short_option(char option, int& needs_value) const
 {
-    Vector<StringView> parts = m_short_options.split_view(option, true);
+    Vector<StringView> parts = m_short_options.split_view(option, SplitBehavior::KeepEmpty);
 
     VERIFY(parts.size() <= 2);
     if (parts.size() < 2) {