handle "too many open files" better

[dnut]

Since polling happens frequently, this error happens every few minutes, which breaks the rust process so it must exit and be restarted:

thread 'main' panicked at 'Sending a message failed.: EMFILE', /home/drew/.cargo/registry/src/jackfan.us.kg-1ecc6299db9ec823/wayland-client-0.29.4/src/rust_imp/proxy.rs:211:39

This is a problem in wayland-rs, see YaLTeR/wl-clipboard-rs#12 and Smithay/wayland-rs#235.

The current solution is to just restart the app with a shell script any time it exits. I'm sure there is a more elegant way to do this.

Ideally the process can clean up its own open files, but I'm not sure there's a way to do this without fixing the library. So we probably have to live with the fact that the process must terminated to close all the files, and then a new process must be spawned.

At the very least we can manage the process by forking from rust instead of bash. Some exit status can be used to indicate why the process had to exit. So when the failure is EMFILE the process can be restarted, but otherwise it can exit the entire service if desired.

[dnut]

simple MVP solution: loop in rust with a fork instead of using a shell script. no conditional error handling