Propagate all logging fields to the tty logger

[jandubois]

The fields are serialized in JSON by the hostagent and then printed by the limactl start command to the console, so need to be explicitly added back to the logger entry.

This PR is in response to #2228 (comment).

Note that nested structures (like events.Event) will be flattened by the standard logger, e.g.

       err := errors.New("oops")
       ev := events.Event{
               Status: events.Status{
                       Running: true,
                       Errors:  []string{"Error one", "Error two"},
               },
       }
       logrus.WithError(err).WithField("events", ev).Warn("Log message with error")

will result in

WARN[0020] [hostagent] Log message with error            error=oops events="map[status:map[errors:[Error one Error two] running:true] time:0001-01-01T00:00:00Z]"

The change to qemu_driver.go is needed to avoid the ugly <nil> error in

INFO[0004] [hostagent] QEMU has exited                   error="<nil>"

@balajiv113 Your inotify PR has additional logging entries with duplicate err which should be changed if this PR is accepted/merged:

pkg/hostagent/hostagent.go
604:				logrus.WithError(err).Warn("failed to start inotify", err)

pkg/hostagent/inotify.go
52:				logrus.WithError(err).Warn("failed to send inotify", err)

[jandubois]

I made one more change to replace the switch lv block with this logic, which feels clearer to me:

if !logger.IsLevelEnabled(lv) {
	return
}
// …
if lv <= logrus.FatalLevel {
	entry = entry.WithField("level", lv)
	lv = logrus.ErrorLevel
}
entry.Log(lv, header+j.Msg)

[jandubois]

@AkihiroSuda Speaking of comments, I think this line could use some explanation:

if !j.Time.IsZero() && !begin.IsZero() && begin.After(j.Time.Add(epsilon)) {
	return
}

It seems to be added by 21b7cb0 to control logging for limactl stop iiuc, and seems to ignore log messages that are more than one second before the begin value.

It is not clear to me why this is needed; I assume if there is still a backlog of unprocessed log messages from before the stop command, that you don't want to dump them out to the terminal?

[jandubois]

I just realized that there are tests in logrusutil_test.go that should be updated too. I won't have time for this for the next few days though, so will turn this into draft for now.

I don't plan on changing anything else but the tests though, so feel free to review the draft code in case you have any feedback!

[jandubois]

I won't have time for this for the next few days though, so will turn this into draft for now.

I added the tests and took it out of draft; I think it is good now.

[AkihiroSuda]

Thanks