* Fix another UAF in skyline
* Simplify
* r_vector_insert() accepts assign at last index
* No need to check for parts that fit/overlap with new_part if new_part itself fitted inside a prev_part
* Add RSkyline ##util
* Add `r_vector_len()`
* Optimize io.cache ##io
* Use RSkyline instead of RList
* Add cache skyline for faster reads
* Use PJ API in `wcj`
* Add test and fix