feat: fanotify filesystem watch (last)

[AntoineGS]

This is still a work in progress and contains added logging/output and code to refactor but it works to give you an idea of what it could be like.

Fixes #538

Todos

• Cleanup logging
• Add mentions for BTRFS in the doc or UI, possibly a warning when detected

[quadratech188]

This looks more like an e-dant/watcher (the external library that provides watcher.hpp) pull request rather than a vicinae pull request, so maybe we should consider contributing to that instead?

[quadratech188]

Technically we could have our own version, but then updating the library would be a nightmare

[AntoineGS]

😲 I had no idea this was an external dep, my bad.
Yeah you are right, I will see about upstreaming the changes and report back on how that goes.

[aurelleb]

I think it's okay to make local edits to our watcher.hpp to suit our use cases, and propose a PR upstream if they are interested.

[AntoineGS]

I am starting to get conflicts in between branches (I try to keep features/fixes separate as much as possible).
Do you have any objections that I branch each PR off another PR and I number them in the order that they should be merged to keep changes separate?