Command parser fixes

[mworzala]

Created from Minestom#1893

[spannercodes]

I've figured out the reason for the argument order bug:

The problem is with the graph generation. See GraphImpl.java line 155 (or all of fromCommand). Basically, it first generates a ConversionNode for the "AB together" syntax, and in doing so adds the argument "A" to the command's children (syntaxNode.nextMap). The executor for "A"'s ConversionNode is set to null, because the converter doesn't know about the "A only" syntax (and so it is doing the right thing to say that "cmd a" would not have an executor).
The issue is that because "A" is already added to the command's children, the graph generator skips it and does not add the newly found executor.

I'm not sure how to fix this yet but I'll keep trying. I think it's going to have to be something horrible, or just rewrite parts of ConversionNode, because currently it's a record and everything is final.

[mworzala]

thank you @spannerdev!