m/pkg/logtree: implement concise stringification

This adds a new method on LogEntry: ConciseString(). It's designed to
be used in cases where we want to display the log line on some
limited-width (and likely non-interactive) log console, like TTY
consoles in Metropolis.

This is a bit too Metropolis-specific to my liking (we hardcode some
logic related to the layout of root.role.*), but it'll do for now.

Change-Id: I1079b8b19a3c304fcc5077ce6b4c69887a34d7ae
Reviewed-on: https://review.monogon.dev/c/monogon/+/1359
Reviewed-by: Leopold Schabel <leo@monogon.tech>
Tested-by: Jenkins CI
diff --git a/go.mod b/go.mod
index 9ec5608..a69c12c 100644
--- a/go.mod
+++ b/go.mod
@@ -100,6 +100,7 @@
 	github.com/mdlayher/genetlink v1.2.0
 	github.com/mdlayher/netlink v1.6.0
 	github.com/mdlayher/raw v0.1.0
+	github.com/mitchellh/go-wordwrap v1.0.0
 	github.com/opencontainers/runc v1.1.3
 	github.com/packethost/packngo v0.29.0
 	github.com/pierrec/lz4/v4 v4.1.14
@@ -290,7 +291,6 @@
 	github.com/mindprince/gonvml v0.0.0-20190828220739-9ebdce4bb989 // indirect
 	github.com/mistifyio/go-zfs v2.1.2-0.20190413222219-f784269be439+incompatible // indirect
 	github.com/mitchellh/go-homedir v1.1.0 // indirect
-	github.com/mitchellh/go-wordwrap v1.0.0 // indirect
 	github.com/mitchellh/mapstructure v1.4.2 // indirect
 	github.com/moby/locker v1.0.1 // indirect
 	github.com/moby/spdystream v0.2.0 // indirect