Catch signals produced by PRED in tree-sitter search functions

Catch signals produced by PRED in tree-sitter search functions

Earlier we switched to using cursors rather than nodes to traverse the
parse tree.  Because cursors need cleanup, we have to catch signals
thrown by the predicate functions and free the cursor. Failing to do
this will result in leaking the cursor whenever the predicate function
signals in a search function.

This change fixes the leak.

* src/treesit.c (treesit_traverse_cleanup_cursor): New function.
(Ftreesit_search_subtree)
(Ftreesit_search_forward)
(Ftreesit_induce_sparse_tree): Catch signals.