fix(lua): reject process exit in fast callbacks #39937

Problem:
`os.exit()` in `nvim -l` exits through normal teardown. But, as #39783 shows,
when it is called from a libuv callback, teardown polling the main loop
when inside `uv_run()` can trip the recursive poll guard and cause a crash.

Fast callbacks are not safe to teardown, so it's better to schedule an exit out
of a callback rather than convolutedly handle this as I tried before.

Solution:
Reject `os.exit()` from fast callbacks with `E5560` error.

0 files changed, 0 insertions, 0 deletions