Instead of trying to build a regular expression string, just build a
structured thing with seq() and choice() and whatnot. This is
technically uglier but fixes a problem I found with comment regular
expressions so you know, it works, which is better than not working.
Also now tokens get named and maybe that's good? It's so hard to say.
This allows most of our precedence to be re-used. There are some cases
still where tree-sitter gets confused (and we don't), see the
corresponding change to grammar.py. I wish I knew how to fix this but
I don't. :(
Tree sitter doesn't let me do token-based precedence? I don't like
tree-sitter's "make it inline but give it a number" system- seems like
a bug farm to me.
