Broaden error!() to cover any user-initiated action that fails to do
what was expected (e.g. failed hotplug or live migration), not only
unrecoverable startup errors. Retarget info!() at operators and users,
clarify the warn!() and debug!() audiences, and document trace!().
Part of #8440.
Co-authored-by: Philipp Schuster <phip1611@gmail.com>
Signed-off-by: Tushar Khatri <hello@tusharkhatri.in>