Make treesit-search-forward-goto accept a NODE argument

Make treesit-search-forward-goto accept a NODE argument

With NODE argument we can do

(setq node (treesit-search-forward-goto node))

And we can choose what node to pass to it (maybe we want to pass it
the largest node at point, rather than the smallest node, and in case
of multiple parsers, we can choose which parser to use).

* doc/lispref/parsing.texi (Retrieving Node): Update manual.
* lisp/treesit.el (treesit-search-forward-goto): Accept a NODE
argument.