Problem:
`TSNode:_rawquery()` is complicated, has known issues and the Lua and
C code is awkwardly coupled (see logic with `active`).
Solution:
- Add `TSQueryCursor` and `TSQueryMatch` bindings.
- Replace `TSNode:_rawquery()` with `TSQueryCursor:next_capture()` and `TSQueryCursor:next_match()`
- Do more stuff in Lua
- API for `Query:iter_captures()` and `Query:iter_matches()` remains the same.
- `treesitter.c` no longer contains any logic related to predicates.
- Add `match_limit` option to `iter_matches()`. Default is still 256.
aca2048bcd