linux: Replace current fs::watch with PollWatcher.

[CharlesChen0823]

Follow with #11595, and comment.

1. Currently, in linux platform, using notify::recommanded_watcher for watch config.json file modify.
2. When using ctrl-shift-p toggle vim mode, will using NamedTempFile to rename with exsit file, notify will emit Modify and Delete event.
3. In current notify default impl, Delete event will triggle watcher remove watch file anymore. Only restart Zed will work for config.json modify.
4. replace with PollWatcher will not cause this problem.

But, there also leave another problem, because linux platform active_window not implement, after modify vim mode, need manual click other tab active vim mode work.

I don't know if this is accept modify.

Release Notes:

• N/A

[ConradIrwin]

@CharlesChen0823 thanks for investigating this!

I don't think we want to use a poll-watcher if fsnotify is available. Can we need to restart the fsnotify if we observe a delete on the settings file instead?

cc @mikayla-maki our linux guru

[mikayla-maki]

@ConradIrwin, that's what the code should be doing already! Sounds like there's a bug we need to fix 🙃

@CharlesChen0823, I don't think we want to use a PollWatcher, as it'll be much slower than inotify. It looks like we're already trying to recreate the file watcher here: https://github.com/zed-industries/zed/pull/11749/files#diff-e13638ad3885e643f14ba8cde1f20fb4955f2cf025ee6b4e7bdb33a0c3f00e50R446-R451, how is the existing solution failing in this case?

[mikayla-maki]

Also, going to close this PR to keep things organized. Feel free to make an issue, or another PR, as we'd like to fix this bug :)