text-minimessage: Use a Consumer rather than Appendable for debug output

[zml2008]

Fixes GH-667

[gepron1x]

May i ask, why do you use null if debug is disabled? Why not just empty consumer?

[gepron1x]

Also, consider adding convenience method to builder that accepts Appendable and sneaky throws IOException?

[kezz]

May i ask, why do you use null if debug is disabled? Why not just empty consumer?

There are some non-zero cost calculations/string formatting that takes place that doesn't need to happen if nobody is caring about the logging.

Also, consider adding convenience method to builder that accepts Appendable and sneaky throws IOException?

I'm not massively interested in adding a convenience method for Appendable, it's a bit of a rubbish class to use and considering how easy it is to wrap in a consumer I don't think we really need to add/encourage use of such a method.