Problem:
vim.ui.open "locks up" Nvim if the spawned process does not terminate. #27986
Solution:
- Change `vim.ui.open()`:
- Do not call `wait()`.
- Return a `SystemObj`. The caller can decide if it wants to `wait()`.
- Change `gx` to `wait()` only a short time.
- Allows `gx` to show a message if the command fails, without the
risk of waiting forever.
57adf8c6e0