feedback: add cmake option to disable the daemon

There is a complaint that the feedback daemon is a 'spying' tool
and because of that can't be used on Gentoo. Its default disabled
option also is not acceptable, the daemon should be eliminated
completely.

The patch introduces cmake option ENABLE_FEEDBACK_DAEMON. It is
ON by default. When set to OFF, all feedback daemon's code is not
included into the binary, its configuration options disappear.

Closes #3308