This implements FileWatcher using inotify filesystem events. Serenity's
InodeWatcher is remarkably similar to inotify, so this is almost an
identical implementation.
The existing TestLibCoreFileWatcher test is added to Lagom (currently
just for Linux).
This does not implement BlockingFileWatcher as that is currently not
used anywhere but on Serenity.
This patch adds some rudimentary tests for InodeWatcher. It tests the
basic functionality, but maybe there are corner cases I haven't caught.
Additionally, this is our first LibCore test. :^)