Userland+AK: Stop using getopt() for ArgsParser

This commit moves the implementation of getopt into AK, and converts its
API to understand and use StringView instead of char*.
Everything else is caught in the crossfire of making
Option::accept_value() take a StringView instead of a char const*.

With this, we must now pass a Span<StringView> to ArgsParser::parse(),
applications using LibMain are unaffected, but anything not using that
or taking its own argc/argv has to construct a Vector<StringView> for
this method.

Userland/Utilities/ttfdisasm.cpp

@@ -190,7 +190,7 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
     }
 
     if (!s_disassembly_attempted) {
-        args_parser.print_usage(stderr, arguments.argv[0]);
+        args_parser.print_usage(stderr, arguments.strings[0]);
         return 1;
     }
     return 0;