sosreport: Port to fsinfo

[martinpitt]

fswatch1 is being deprecated. This also gets rid of the ugly find | xargs stat shellery, as fsinfo gets us the modification time.

fsinfo also gives us an initial 'change' event, so we don't need the "initial" and "on change" handler duplication.

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This by and large works fine, but there is something really concerning: Instantiating an FsInfoClient breaks an existing fswatch1 channel (which I could still understand, somehow interfering inotify's -- even though it should work). But it also breaks the

superuser.addEventListener("changed", restart);

this never gets called any more. The D-Bus notify signal itself works, but cockpit.js then messes it up. This is somehow related to the new Transport and Channel classes.

Debugging note for myself:

grep -lrw preload /usr/share/cockpit | xargs sed -i '/\bpreload\b/d'