[REQ] Add support for JAX FFI

[nvlukasz]

Description

JAX FFI is a new callback mechanism available since JAX v0.4.31. It offers improved CUDA graph support and Warp should switch to FFI from the original custom_call approach.

Context

[nvlukasz]

Merged in a15d3b6

[chaoming0625]

Hi, I am wondering what does improved CUDA graph support mean?