Fix treesit_cursor_helper (bug#60267)

Fix treesit_cursor_helper (bug#60267)

The cause of that bug is that in a particular parse tree, the node
treesit_cursor_helper tries to go to is a missing node, not only is it
a missing node, it is the first node of a subtree.  So when
treesit_cursor_helper follows the algorithm and goes down the tree, it
goes down the previous subtree (because that subtree's end = end_pos,
because the target node has zero width).

    o
    |
 o--+-o
 |    |
 +-+  +-+-+
 | |  | | |
 o x  t o o

(We ended up in x when the target is t, because t has zero width.)

One way to solve it is to go back up the tree if we are at a leaf node
and still haven't matched the target node.  That's too ugly and
finicky so I resorted to recursion.  Now one more functions will
return give up (treesit_node_parent) if we are in a werid parse tree
that is super deep.  But since we already kind of give up on this kind
of parse trees (bug#59426), it doesn't really hurt.

* src/treesit.c (treesit_cursor_helper_1): New function.
(treesit_cursor_helper): Use the new function.  Change return type to
bool, and accept a cursor pointer.

(Ftreesit_node_parent)
(Ftreesit_search_subtree)
(Ftreesit_search_forward)
(Ftreesit_induce_sparse_tree): Use the new signature.