Handle signals gracefully in tree-sitter query predicates

Handle signals gracefully in tree-sitter query predicates

Before this change, predicate functions can signal, which will cause
Ftreesit_query_capture to skip freeing the query and cursor object.
We make predicate functions return the signal data rather than
directly signal.

* src/treesit.c (treesit_predicate_capture_name_to_node)
(treesit_predicate_capture_name_to_text)
(treesit_predicate_equal)
(treesit_predicate_match)
(treesit_predicate_pred)
(treesit_eval_predicates): Return signal rather than signaling
directly.
(Ftreesit_query_capture): Check for returned signal data.