Make use of the new pred shapes in treesit.el

Make use of the new pred shapes in treesit.el

treesit-search-forward and friends now accept more shapes for PRED,
make use of it in navigation functions.

* lisp/treesit.el (treesit-node-top-level): Use treesit-node-match-p.
(treesit--thing-unpack-pattern): Remove function.
(treesit-beginning-of-thing)
(treesit-end-of-thing): Remove PRED argument.
(treesit--things-around): Remove PRED argument, use
treesit-node-match-p.
(treesit--top-level-thing): Remove function.
(treesit--navigate-thing): Remove PRED argument.
(treesit-thing-at-point): Update docstring, don't unpack PATTERN.

* test/src/treesit-tests.el:
(treesit--ert-test-defun-navigation): Don't unpack pattern.