LibCore+Everywhere: Remove ArgsParser::add*(char const*&)

This is not guaranteed to always work correctly as ArgsParser deals in
StringViews and might have a non-properly-null-terminated string as a
value. As a bonus, using StringView (and DeprecatedString where
necessary) leads to nicer looking code too :^)

Userland/DevTools/HackStudio/main.cpp

@@ -54,7 +54,7 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
         TRY(notify_make_not_available());
     }
 
-    char const* path_argument = nullptr;
+    StringView path_argument;
     bool mode_coredump = false;
     pid_t pid_to_debug = -1;
     Core::ArgsParser args_parser;