Delimiter scanning takes into account too many delimiters

When scanning for delimiters, we can sometimes scan for delimiters that we shouldn't. See test delmiterScanning_03 in SequenceGroupDelimiters.tdml as an example where we scan for comma separator that, while it is in scope, should be ignored because the element is the last in the sequence with an infix separator.

I've confirmed that the DelimitedStringParser scans for and finds the wrong delimiter, but it's possible that this is a problem in the delimiter stack. Perhaps we need to manipulate the delimiter stack when we determine that the current scope of delimiters should be ignored due to being the last in the sequence? With the correct stack, all the delimiter scanning and delimite consuming sould just work.